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The UK’s best-selling aquatics magazine
How to keep
the world’s
favourite
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Soften up
What water
hardness is and
why it matters
Q&A
Halfbeaks, Corydoras,
Fan shrimps,
& more
September 2018 £4.50
3
great gobies
Freshwater oddities
you’ll love to try
Rusty catfish
The gentle giant that
eats wood!
Get smart
The amazing world
of brainy fish
Pearl eartheaters
How to keep and
spawn Geophagus

ContentsSeptember
32
Win
AN ALl pond solutions
fish tank & cabinet set
worth £499.99
Page 74
92
08
14
24
32
Inspiration
MASTER OF DIsguise
Meet the blackwater-dwelling
Pikehead, which does a mean
impression of a floating twig,
then catches its prey in its
incredible protrusible mouth.
orchestra of angels
From common species to
amazing Altums, this month’s
species showcase is a real
angel delight.
in rust we trust
How one stunning underwater
photograph made PFK editor
Nathan see the Rusty plec – a
fish he thought he knew only
too well – in a whole new light.
How smart is a fish?
Can fish learn? Can they
navigate? Use tools? Form
40
46
68
friendships? Chris Sergeant
pulls together a variety of
scientific studies to investigate
the cognitive powers of fish.
the little pearl
eartheater
Top tips on how to keep and
breed this attractive and
rewarding little cichlid.
a natural mix
In a world of cultural diversity,
what’s to stop us mixing fish
from different continents in one
simple planted tank? Follow our
step-by-step guide…
PRETTY DAMSELs
For years, damselfish have had
a bad press, but some really
don’t deserve their bully
boy reputation. They
could be just the
marines you’re looking for.
Editor’s
Pick
Read Editor
Nathan’s favourite
article this issue
– Meet the gobies
on page 76!
76
82
10
10
22
MEET THE GOBIEs
Introducing three freshwater
species of goby perfectly suited
to life in the home aquarium.
MAKE SPACE FOR RAYS
Extraordinary and enigmatic,
stingrays are the ultimate
freshwater fish for the specialist
keeper with room(s) to spare.
News & Views
Fishkeeping news
Why Blind cave tetra from
Mexico might offer an insight
into human eye conditions,
summer drought alert for native
fish, and the Great white shark
spotted holidaying off Mallorca.
Ethical debate
PFK editor Nathan and writer
Steve go head to head on the
subject of tank decoration – is it
6 PRACTICAL FISHKEEPING

5
things
you will
learn in
this issue
How smart your
1 fish is and what
it’s capable of
thinking about.
How to use the
2 Pearson’s Square
to work out your
water hardness.
3How to get your
tank squeaky
clean with our Q&A
on cleaning gravel.
4Identify the
different varieties
of the common angel.
5How to set
up a natural
community tank
with seven different
types of plants.
53
24 14
28
92
98
104
just a matter of taste or a more
serious question of welfare?
LETTERS
Surprise baby Pandas, a plea
for more pond fish features, and
a sad warning for fish lovers to
double-check their equipment.
Gear & Reviews
Roadtrip
The PFK team visits aquatics
shops in and around Newcastle
and County Durham.
THE BIG POND
AIRPUMP TEST
We test a selection of ‘big gun’
pond airpumps for all budgets.
108
53
62
USED & ABUSED
New product news and the
latest gear tried and tested.
This month: a versatile, multiuse
Biopod, a new tinned fish
food range from Arcadia, and
a funky nano aquarium that’s
child’s play to maintain.
READERS’ POLL 2018
Vote for your favourite UK
aquatics shop – and enter our
free prize draw with Fluval gear
up for grabs.
Regulars
Fishkeeping answers
PFK’s crack team of aquatics
experts are on hand to answer
all your questions. This month:
Fan shrimps, emergent plants,
breeding marine gobies, and
fish as pets, to name just a few.
Fishkeeping know-how
All you ever wanted to know
about water hardness – what it
is, how to measure it, and how
Practical
Fishkeeping
delivered to
your digital
device
page 66
66
74
75
114
best to manipulate it to suit the
fish you keep.
Subscribe to PFK
Get two years of Practical
Fishkeeping for the price of
one – and never miss an issue.
COMPETITION: WIN A
350l tank & CaBiNET
Enter our free prize draw to
win a fabulous, stylish tank
and cabinet set from All Pond
Solutions, worth £499.99!
Next month
Celestial pearl danios, setting
up a shooting gallery for
Archerfish, and Otocinclus.
Tailpiece
Nathan muses on stingrays
and stingray keepers – and the
merits, or otherwise, of being a
trophy fish.
www.practicalfishkeeping.co.uk 7

Fascinating Fish
Pikehead
Master of
disguise
It’s not big, it’s not rare, but the picky Pikehead
is a real challenge to keep.
WORDS: steve baker
In a split second, the Pikehead shoots its
protrusible jaws forwards, extending its mouthparts
up to one third the length of its body
8 PRACTICAL FISHKEEPING

It’s amazing, the
conditions some fish have
naturally adapted to live in.
Stagnant water is enough
to worry any fishkeeper,
but add a pH reading as
low as 3.0 and you might
assume there could be no
fish alive in water like that. But not
only are there fish alive in these
conditions, there are predators
that thrive in them.
The Pikehead, Luciocephalus
pulcher, inhabits the still blackwaters
of Southeast Asia. They can be
found in very calm, flowing areas of
blackwater streams, but more often
they’re found in peaty swamps with
overhanging forest canopy. There
are huge amounts of broken-down
organic matter in the water, not just
from the ancient peat, but also from
the falling leaf litter of the forest.
This dark tannin-staining
dramatically cuts the light that can
penetrate the water, so no plants
live here, but the Pikehead is an
ambush predator. It preys by
floating motionless in the
top section of the
water, giving the
impression it’s just
another twig
that’s
fallen from the canopy above.
During the wet season, when
the forests are in flood, L. pulcher
adopts aquatic and floating plants
as its ambush hides.
It may surprise you to know this
fish is closely related to the
Chocolate gourami, Sphaerichthys
osphromenoides. Like the gourami,
the Pikehead is a mouthbrooder
with a labyrinth breathing organ.
The Pikehead and its cousin the
Peppermint pikehead, Luciocephalus
aura, are the only obligate predators
of the anabantoids and these
fellows love shrimp.
To catch its meal, this fish has
an impressive weapon – blink and
you’ll miss the strike. In a split
second, the Pikehead shoots its
protrusible jaws forwards,
extending its mouthparts
up to one third
the length of its body.
Unfortunately, the niche
adaptations this fish has developed
are the downside to keeping them
in tanks. First, they’re delicate and
don’t travel well; second, newly
imported Pikeheads are rather
ragged-looking and take time to get
feeding; and third, they commonly
suffer from bacterial infections –
there’s little bacterial life in the
highly acid conditions of their home
waters, so their immune system
isn’t well developed.
They’re also notoriously difficult to
wean off live foods, so you have to
accept they may well need live
foods permanently. And then there
are the water parameters – with a
pH any higher than 6.0, they’re likely
to struggle with bacterial infections.
But if you like a challenge, then the
Pikehead’s your fish.
Above: Short
body, big head.
MAIn: The
Pikehead’s
huge, protrusible
mouth engulfs
its prey.
Alamy
shutterstock
www.practicalfishkeeping.co.uk 9

Opinion
Nathan hill & Steve baker
Love them or hate them, a lot of aquarists enjoy setting up a
tank with the kind of decoration that makes Las Vegas look
bland. We discuss whether that even matters...
Jacques Portal
Some tanks are so bright that
they capture your attention
whether you want them to
or not. Bright pink gravels
are sold for a reason – they’re
popular – as is the galaxy of
garish, glow-in-the-dark,
LED-studded ornaments on
the market. But do we ever stop to think
about the fish, and whether they’re really
enjoying all our day-glo antics? Should
we be trying to create natural-looking
tanks, or do our fish simply not care?
SB: I’m always a fan of naturalistic set-ups;
that’s no secret and I see fish respond
beautifully in this situation, in their health,
colouration and beh aviour.
Even as an eight-year-old with my first
tank I chose pea shingle gravel and
slate pieces to build a
cave. But I don’t want
to spoil other people’s
fun or discourage
anyone from the hobby
so I don’t mind seeing
coloured gravels and
ornaments. I do worry
about glow-in-the-dark
or some of the lighting
in tanks though.
Have you ever had a
colourful tank?
NH: I’ve set up ‘gimmicky’ tanks in the past,
though mainly out of necessity. In my retail
days, we would often set up display tanks
with multiple air-driven ornaments (divers,
treasure chests and so on), all kinds of bright
gravel and anything else you can imagine.
It was a sales pitch, and the tanks were filled
with equally garish fish – guppies and fancy
goldfish mainly.
With hindsight, those fish were not in the
best way. They were stressed out, prone to
disease and, I suspect, suffered a higher
mortality rate than the fish in the sale tanks.
An alien world
where colours
don’t make sense,
smokey lasers
dance around us,
and beeps disturb
our sleep...
While I think there’s a time and a place for
the personal touch on our tanks, I worry if
these aquaria are actually compromising
fish welfare. If they are, then there’s a case
that can be made against them.
SB: It would be nice to see a study done to
see what does and doesn’t stress fish in this
respect. I know if you light a tank from the
bottom, it sends fish loopy and they swim
on their sides – that’s why I worry about
glow-in-the-dark stuff and LED pieces.
I wouldn’t mind betting that the noise and
vibrations from air ornaments upset them too.
Actually I do remember a study on tank
background colours that concluded freshwater
fish are less stressed with darker, natural
colours like black, brown, dark green and
grey. That’s why it always beats me that so
many shops use bright blue.
NH: Yeah, I think that’s
where we might find our first
paradox. I recall seeing
studies involving fish in
research facilities (Danios, I
think) given a choice
between bare tanks and
tanks with enrichment – tank
decorations. They would
always spend more time on
the enriched side, regardless
of how sparse and what kind
of decoration was used. So
at face value it seems fish prefer having
something in their tanks, rather than nothing.
We do know that some fish are happy with
darker substrates. I wonder how something
like a Banjo catfish, which usually buries itself
for camouflage, would feel about being
embedded in ‘clown vomit’ multicoloured
gravel. Surely it would have some innate
sense of ‘This isn’t quite right…’?
Is it fair to say that some fish are better
suited to life in an ‘artificial’ layout than
others? And if so, what kind of fish do you
think would be unsuitable for such a tank?

SB: I would imagine suitable fish for a
multicolour tank would start and end at
farmed fish that have had generations of tank
breeding – and even then I would think any
naturally camouflaged fish would be
unsuitable. Guppies, platies, mollies, neons
(especially Gold, Diamond and do on), albino
corys and fancy goldfish would strike me as
the most suitable and probably appeal to the
same people that go for day-glo. I’m sure a
wild-caught fish would break out in whitespot
just thinking about it. I guess most shrimp
and snails would be OK too.
is the way. We could relate it to dog breeds
heavily removed from their original ancestors
and their lack of natural stimulation, but why
should we do it wrong because they do? It’s a
question of money mostly I guess (and not
just from ornament sales), but if we said ‘It’s
wrong, you can’t do that’, how many now
experienced aquarists would never have
started fishkeeping? How many biotope
boffins and artistic aquascapers started off
with gaudy? And would they have started if
gaudy wasn’t available? And would there be
enough readers to keep you and me in a job?
NH: You see, the more I brood on it, the more
I’m starting to think that no fish is really
suited to such a tank. I’m even thinking of
manufactured hybrids like Parrot cichlids, fish
that have experienced only artifice their whole
lives, who are still being denied inherited
behaviours from their cichlid ancestry. I’ve
seen Parrots trying to dig sand bowers, as is
written into their DNA, and failing
to do so with pink gravel.
Admittedly, fish like
platies appear oblivious
to their surroundings
– as long as they
have a full belly and
something to breed
with, they seem
happy. But then
there are other
issues for them.
Platies are nearconstant
grazers, for
example, nibbling at
surfaces all the time.
I’ve seen them in the past
nibbling away at ornaments,
slowly grazing through the paint and
resin coatings. I’d imagine that anything that
rasps surfaces – suckermouth cats, say –
would be a similar worry. I only have
anecdotal evidence to offer, but I’ve seen
enough mysterious and premature
suckermouth deaths in such decorated tanks
to think there could be a link.
But here’s the curve ball. Shouldn’t we be
striving to provide the best for our fish? And
seeing as they’ve evolved to fit certain habitat
niches perfectly, is it not fair to say that
recreations of those niches would be the best
habitats for them to live in?
SB: We should be providing the best for our
fish, yes. I’m no fan of line-bred fish, as you
know, so for me natural tanks and natural fish
Alamy
NH: There’s definitely a sacrificial lamb
aspect to it all. My first tank was shocking
– rocky cave, every colour of gravel available
at the time, tacky plastic plants in pink and
purple, and a deformed goldfish. In my
defence, I was four at the time.
I’d call it a learning curve. I didn’t really get
into biotopes, or at least themed tanks
(Tanganyika, brackish and so on) until
I was riding my teenage years.
I’m actually torn here now.
A couple of months back
I was defending folks who
had bright and unnatural
tanks, on the grounds
that as long as the fish
were happy, we could
all be happy.
But I’m calling
that happiness into
question. I think there
is such a thing as a
step too far here. Like it
or not, fish have adapted to
live in certain environments.
Much as certain insects have
evolved to emerge from pupation fully
equipped with the knowledge of how to feed
from certain flowers, or parasitise certain
other insects, so I imagine that fish have some
‘innate’ hardwired memories – ways to
behave in and around plants to avoid
predation, how to swim through open water,
and so on. I believe that even captive-born
fish have this same hardwiring.
Taking such a fish and sticking it into a
typically Disney-style aquarium can’t be
much better than taking you or me and
throwing us into an alien world where colours
don’t make sense, smokey lasers dance
around us all day, and insane chirrups and
beeps disturb our sleep.
We’re not going to agree on this one. I think
we can do better for our fish than bright pink.
Inset: Do
goldfish really
care about the
tank they’re in?
Do you have an opinion on tank decoration that you would like to share or
perhaps a topic you would like to see discussed? If so, you can find us at
www.facebook.com/pfkmag or email editorial@practicalfishkeeping.co.uk

Know-how
Advice
Water
hardness
It’s one of the most important factors in successful fishkeeping, but
what exactly is it – and, more importantly, how can you manipulate it?
WORDS: steve baker
Now, here’s a
subject that every
aquarist should have
at least some grasp
of, but many don’t.
The ins and outs of
water hardness can
be unnecessarily
complicated by several different
scales of measurement – it’s also
information that shop staff don’t
tend to offer, or maybe don’t always
totally understand themselves.
Let’s set out one thing to start
with: here at Practical Fishkeeping
we talk in German degrees of
hardness (GDH), and there are two
measurements of GDH – General
Hardness (°GH or just °H) and
Carbonate Hardness (°KH).
You may see also hardness
referred to as PPM (parts per
million), Clark (English scale)
degrees of hardness, French
degrees, or written as ‘soft’,
‘medium-hard’ and so on.
As with most things now, a quick
scan of the internet and you can
find water hardness conversion
charts/websites should you
come across hardness expressed
in a measurement you’re not
familiar with.
KH is a measurement of
carbonate and bicarbonate anions
in the water; GH is a measurement
of calcium and magnesium ions.
KH is important as it buffers/
stabilises pH (acid/alkaline) as the
Soft water fish in hard water
The concentration of minerals in the
water is higher than the concentration of
minerals in the fish. This means that the
fish is constantly being invaded through
the gills and skin by minerals trying to
even out this imbalance.
Hard water fish in soft water
The concentration of minerals in the
water is lower than the concentration of
minerals in the fish. This means that the
fish is constantly being drained from the
gills and skin of minerals that are trying
to even out the imbalance.
Soft water fish in Hard water
In order to flush excess minerals from
the body, the fish needs to increase its
gill and kidney activity, which requires
energy. This in turn can stress the fish,
and draws energy away from other vital
roles such as immunity.
Hard water fish in soft water
Hard water fish have few mechanisms
by which to retain their mineral content
when placed into mineral-deficient
water. They start to lose essential
electrolytes and other minerals, and this
will eventually weaken and kill them.
If the water is much lower in salts than ideal,
the fish is almost in danger of being ‘diluted’…
increasing physical stress by needing to pump
more water to retain the salts in its body
shutterstock
62 PRACTICAL FISHKEEPING

Buffers
Combined aquatic GH/KH
mixes
For: Ease of use.
Against: An assumed ratio
suitable for most situations.
Pharmacy Sodium Bicarbonate
+ Epsom salts
For: Low cost, ideal ratios can
be achieved.
Against: Very basic salts, no
instructions for aquarium use.
Hardness
scale
in relation to fish
Over 30°H =
very hard
Some Tanganyikan
cichlids – Frontosa,
Fairy cichlid and
Etroplus genus
Individual aquatic GH/KH buffers
For: Ideal ratios can be
achieved, high quality salts.
Against: More involved to use,
higher cost.
Trace
elements
For the icing
on the cake
you can
add trace
elements
– some are
even aimed
at specific
fish or
locations.
18-30°H = hard
Rift valley cichlids
and many
brackish fish,
Rainbowfish
(12-25°H)
12-18°H = fairly hard
Danios, common livebearers
barbs, loaches (8-18°H)
Alamy
carbonates and bicarbonates cling
to and bind up loose hydrogen ions
(H+) that would acidify the water.
The higher the KH, the more acidic
ions can be ‘absorbed’ before the
buffering capacity is overwhelmed
and conditions turn acidic.
KH & pH
KH is not the same as pH
by a long way, but
there is a close
relationship. As a
generalisation,
the higher the
KH, the higher
the pH will be.
Although GH has
little impact on pH, it is
very important for the bodily
functioning of fish in respect of
osmosis. The fish’s watery
environment is constantly trying to
‘dilute’ the fish, while the fish is
constantly holding in salts and
pumping out water. If the
environment is much higher in
dissolved salts than the fish is used
to, its physical stress is amplified by
pumping out salts. If the water is
much lower in salts than ideal, then
Treat rainwater before use to
absorb pollutants. Run it through
carbon (slowly) or sit a bag of
carbon in a bucket of
rainwater for 2-
3 hours.
the fish is almost in danger of being
‘diluted’, not having enough salts in
its body and increasing physical
stress by needing to pump more
water to retain the salts. This leads
to a weakened immune system,
organ failure and possible alkalosis/
acidosis respectively.
Universal solvent
Pure water is the most
universal diluting
agent (or solvent)
on the planet.
As pH neutral,
water will
dissolve both acidic
and alkaline items but,
as it dilutes them, it also
absorbs them, turning water
into a soup of different
minerals, acids, gases and so on,
and altering the way it will react to
whatever it comes into contact with
further down the line. There is a
certain capacity of what water can
carry. Once it is ‘full’ it won’t
dissolve anything more and
previously dissolved items may
even fall out of suspension, back
into a solid form.
8-12°H =
medium hard
Central American
cichlids, tetras,
rasboras (4-12°H)
4-8°H = soft
Boraras, Killifish
Apistogrammas (0-8°H)
0-4°H = very soft
Altum angelfish, Discus
www.practicalfishkeeping.co.uk 63

Know-how
Advice
How do we alter
what we have?
If the water running out of your tap
is soft, you’re in luck. You can use it
just as it is for acid-loving fish, and
it’s easy to dissolve buffers in it
when you want to keep harderwater
fish, or just to add a little for
some stability. Leaf litter and peat
filtration will have a profound
acidifying effect, so be careful with
them – little by little.
However, the majority of
fishkeepers in the UK will have
some level of hardness in their tap
water – mine reads KH 9, GH 15
with a pH of 7.8-8.0. In this case,
it’s futile trying to soften the
water by adding items such
as softening pillows and
pH down remedies,
and although using
peat filtration
will give you a
lower KH, the
high GH remains.
It’s far more
effective and advisable
to remove minerals first,
filtering through a reverse
Clean an area of rock and
put vinegar on it. If it bubbles/
fizzes, it has alkaline minerals
that will alter water
chemistry.
osmosis (RO) unit. You can do
this at home, buy RO water
from a local aquatics
shop or collect and
treat rainwater.
Once you have
soft water, it’s
your choice to
either add buffers
or mix it with your
tapwater for the desired
level of minerals.
Most of my tanks at home
get a 50/50 mix of RO and
tapwater, resulting in KH 5, GH 8,
with a pH of 7.0-7.2. If you need to
bring down pH levels further, a
relatively easy way to do this is by
adding home-made blackwater
extract, leaf litter or using
commercial pH lowering
treatments.
For help in achieving a desired
level of hardness by mixing water,
see the Pearson’s Square chart on
the opposite page.
ABOVE:
A hard water
tank with
calcium-rich
rock and gravel.
opposite
page:
A soft water
tank with acid
leeching wood
and leaf litter.
WHAT HAPPENS IN YOUR TANK
PlantS
Use carbon dioxide,
produce oxygen with
light – pH increases
Use oxygen, produce
carbon dioxide with
darkness – pH decreases
Fish
Breathe in oxygen,
produce carbon dioxide –
pH decreases
Bacterial action
Oxidising nitrogenous
waste binds up oxygen –
pH decreases
Bacterial growth
depletes buffering
capacity – pH decreases
Wood, leaf litter & peat
Leach humic and tannic
acid – pH decreases
Rock/substrate
Some rocks and gravels
harbour calcium, lime,
chalk and so on that slowly
leach – pH increases
64 PRACTICAL FISHKEEPING

neil hepworth
How to use a Pearson’s square to mix Ro and Tapwater
Write down the hardness (in degrees) of your tapwater in box X.
Write down the hardness of your RO water in box Y. Write down
your desired water hardness in box Z.
Now subtract the number in box Z from box X. Write this
number in the bottom right hand box. This is how many parts
of RO water you need to make your mix.
Add the number in box Y to the number in box Z, and write
this number in the top right hand box. This is how many parts
of tapwater you need to make your mix. Make a mix of water
using these proportions to create the hardness in box Z.
Tap water
hardness
Proportion of
tap water
X
Y + Z
Desired water
hardness
Z
RO or
rainwater
hardness
Proportion
of RO or
rainwater
Y
X - Z
20° dH
0° dH
5° dH
5 units
tapwater
15 units
RO or
rainwater
EXAMPLE
Hardness of
your tapwater
.......................
Hardness of
your Ro or
rainwater
.......................
Your desired
water hardness
.......................
Parts needed
.......................
Parts needed
.......................
www.practicalfishkeeping.co.uk 65

TROPICAL
Hypostomus cochliodon
In rust we trust
While they’re no Zebra plec, the Rusty plecs of South America might
be the peaceful community fish you never knew you wanted.
WORDS: nathan hill
marcelo Krause
Factfile
Spotted rusty plec
Scientific name: Hypostomus cf. cochliodon
Pronunciation: High-poss-tow-muss cok-lee-oh-don
Size: 18cm
Origin: Quite widespread throughout Brazil and Paraguay,
possibly reaching into Argentina
Habitat: Seems to prefer relatively slow-flowing areas of
clear waters
Tank size: Minimum 120x30x30cm
Water requirements: Softish, slightly acidic water preferred;
6.2-7.2 pH, hardness 4-12°H
Temperature: Prefers to be between
22-25°C
Temperament: Peaceful
Feeding: Must have wood in the tank
to graze on. Hardwoods such as apple
are recommended
Availability and cost: Not so common;
from around £25
108 l+
24 PRACTICAL FISHKEEPING

Isn’t it remarkable how a single photo can
change your opinion of a fish? Years ago, when I
worked in aquatic retail, I would buy from a
specialist supplier. We had a deal set up to help
ease my carrier costs – after all, big, heavy boxes
of fish with their demands for careful handling are
expensive to transport, and once the expense of
just a couple of boxes has been divided up
between a few dozen fish and added to the mark-up,
things can really trickle down to the customer.
The deal we had was that I paid for the freight, but
with every order I would get some extra fish with a retail
price equivalent to the cost. I could break even with
each delivery. A superb idea, in principle.
For about eight months in a row, I was sent nothing but
‘Rusty plecs’. I had them everywhere, from large sumps
down to guppy tanks; from crammed into Rainbowfish
displays to fighting Synodontis in catfish communities
where they didn’t belong. I could have eaten for free,
and well, if Rusty plecs had been on my menu.
I pleaded for a different fish; something I could sell,
something that was more exciting than these doorstops
of armoured brown flesh. Eventually the supply waned,
and over some years I sold my glut of Rusties. But that
experience had left me jaded. Here was a fish I would
never keep again, if I could help it.
Then I stumbled across the photos of Marcelo Krause,
a nature photographer from South America. I was given
access to a private gallery, adorned with his aquatic
work. And there, in the middle of shots of tetras shining
like precious stones, and balls of spawning Pimelodids,
I saw my old nemesis – one of the Rusty plecs I loathed
so, but in a new light. This was not the unwieldy
lummox I remembered crashing about my tanks
and never selling.
This was a revelation. A Hypostomus catfish casually
lounging on a piece of fallen, eroded wood, unrattled
by the photographer and oblivious to the diver creeping
up behind him.
Looking closer at the wood, I saw it was covered in
bivalves – freshwater mussels that call South American
rivers their home. I was enamoured. I’d never even
imagined these fish as having a natural home; to me they
were an overabundant nuisance, maybe churned out by
eastern farms. Yet here they were, wild. Wild and glorious.
I dug deeper. Maybe it was time to get to know the
fish I had rejected so many times before. For the first
time in my life, I found myself searching through books
for information on them, and digesting reams of
scientific papers.
A Spotted rusty plec
poses for Marcelo
Krause’s camera.
www.practicalfishkeeping.co.uk 25

TROPICAL
Hypostomus cochliodon
Rusty complex
So who are the Rusty plecs? They’re
fish belonging to what’s called the
Hypostomus cochliodon complex,
which started as a group of eight
fish that were all originally clustered
in the scientific genus Cochliodon.
Subsequent revision showed them
all to be Hypostomus species (much
like the so-called ‘common’ plec,
Hypostomus plecostomus) and all
eight were renamed before being
joined by a couple more species
described in 2010.
To look at, they share a few
Factfile
Blue-eyed redfin
rusty plec
Scientific name: Hypostomus soniae
Pronunciation: High-poss-tow-muss
sonn-ee-ay
Size: 30cm
Origin: Rio Tapajos, Brazil
Habitat: Pools and slow-flowing rivers,
always around fallen wood
Tank size: Minimum 150x45x45cm
Water requirements: Softish, slightly
acidic water preferred; 6.2-7.2 pH,
hardness 4-12°H
Temperature: Prefers to be between
24-28°C
Temperament: Peaceful
Feeding: Must have wood in the tank to
graze on. Hardwoods such as apple
recommended
Availability and cost: A little rarer than
the others; from around £35
features. First, as adults they have
high backs, to the point of looking
hunched. Flip them over and look in
the mouth and a trained eye will
spot a fascinating thing –
curious teeth. For most
members of the genus,
the teeth are
spoon-shaped
and have
evolved for one
purpose alone
– rasping at wood.
All fish in the H.
cochliodon group are
termed ‘xylophores’, which
is to say they’re wood eaters.
They’ve evolved this trait to cope
with the often dark waters they
inhabit. Where light is scarce, so too
are the algae, aufwuchs and plant
life that suckermouth cats crave.
This makes them rather messy
fish. In the right tank, they’ll rasp on
wood all day, every day, slowly
digesting the nutrients contained
within, and passing out a rich
lumber dust. Speaking from
experience, Rusty plecs are more
than capable of sullying substrates
and clogging filter foams.
Second, they’re prone to starvation.
In a tank without wood, they are
entirely at the whim of the aquarist
If you want to see plecs
regularly in your tank, don’t put
their wood at the back –
bring it forwards to
show them
off.
to provide all they need. Greenfoods
are often relished – courgette,
broccoli and the like – though tablets
and wafers hold less interest.
Third, and worst of all, I’ve
known Rusty plecs to
poison themselves.
Ornamental resin
decorations,
covered with
bright paints and
varnishes, pose
no obstacle to
wood-rasping teeth. On
more than one occasion
have I seen a dead fish,
apparently full-bellied and lacking
symptoms, in a tank where garish
decoration has been scraped bare.
Suckermouth trio
In the UK we only see three species
brought in with any regularity. Most
common is the standard Rusty plec,
Hypostomus cochliodon, and easily
spotted due to its unique markings
– a dark body with lighter, rusttinted
fins, and toffee-light streaks
emerging from behind each eye.
Then there’s the fish I fawned over
on the previous pages. This is the
Spotted rusty plec, Hypostomus cf.
cochliodon. It is a harder fish to find,
but given away by being a halfway
marcelo Krause
Not a shy fish
in the wild or in
aquariums.
300 l+
Pale blue eyes
and red finnage
attract us
fishkeepers.
nathan hill
26 PRACTICAL FISHKEEPING

Only animals that eat living wood
are called xylophores. Technically,
because Rusty plecs graze on
dead wood, they should be
classed as saproxylic
instead.
house between a true Rusty plec
and a spotty imposter. Look at the
face in young fish, and you’ll see
spots. As the fish ages, and the back
arches, these spots will become
abundant over the body too.
Then there’s the most coveted
gemstone of the bunch: the Blueeyed
redfin rusty plec, Hypostomus
soniae. The description is right there
in the name – burnt orange fins and
a pale sapphire eye make this fish.
Good behaviour
So are Rusty plecs any good for
communities? Actually, yes, so long
as the tank is a little on the large side.
Unlike some suckermouths, Rusties
don’t become territorial, hogging a
branch or cave for themselves and
chasing all else away. You can even
keep them with other suckermouths
and they’ll be the last to put a fin out
of step. They tend not to be skittish
or nervous, and are less likely than
many to take a sudden panic attack
out on your decor.
But like other substantial suckers,
they aren’t exactly tiny. Adult sizes
between 18 to 25cm are the norm,
neil hepworth
so a big tank is needed. Anything
smaller than 120cm is a no go.
The only other worries you have
are feeding and cleaning. No matter
how you dress it up, they need wood
to survive, not to thrive, and without
it they’ll go downhill pretty fast.
With it, they become living sawmills,
pumping out tiny wood chips as
faeces, and you’ll definitely notice
the dusty layer forming in your tank.
But keep on top of that and you’ll
get the dual rewards of big presence
and unique markings. With
hindsight, if I’d looked at my surfeit
of Rusties with the rose-tinted
glasses I have now, I’d have sold
them to all and sundry.
The common
Rusty – more
than meets
the eye.
Factfile
Rusty plec
Scientific name: Hypostomus cochliodon
Pronunciation: High-poss-tow-muss cok-lee-oh-don
Size: 25cm
Origin: Only found in the upper two thirds of the Rio Paraguay
system of Brazil and Paraguay
Habitat: Slow to mid-flowing rivers, always around fallen wood
Tank size: Minimum 120x45x45cm
Water requirements: Soft, slightly acidic
water preferred; 6.4-7.5 pH, hardness
4-15°H
Temperature: Found between 21-27°C
Temperament: Peaceful
Feeding: Must have wood in the tank
to graze on. Hardwoods such as apple
recommended
Availability and cost: Relatively common;
from around £25
240 l+
www.practicalfishkeeping.co.uk 27

Opinion
Nathan hill
Keeping stingrays is a niche
fascination, for sure. And despite
the advent of prodigiously bigger
tanks – and big ideas – it’s probably
best if it stays that way…
Nathan Hill
is Practical
Fishkeeping
magazine’s
associate editor,
biotope fancier,
aquascape
dabbler and
part-time amateur
skateboarder.
Are stingrays
tankbusters? The freshwater
ones, I mean. I’ve been
brooding on it since I read
Dave Wolfenden’s (really
good) feature on them on
page 82 this month. And,
moreover, will I end up
alienating readers if I say that they are?
I guess that’s a risk that comes with the
territory of formulating my thoughts.
Many successes
I recall a discussion that came up with an
avid stingray fan a while back. He couldn’t
understand why freshwater stingrays were
being classed as tankbusters at all. His
reasoning was that so many folks are
keeping them successfully – and not just
keeping them, but breeding them as well.
Now I can’t deny that stingrays are being
bred in prodigious numbers. But I wonder
if this stingray fan was confusing what
makes a tankbuster? It’s new to me to
Stingrays in an
indoor pond.
classify a tankbuster as a fish that doesn’t
breed readily in the home aquarium.
Breeding activity doesn’t necessarily
correspond to welfare at all, of course. I’ve
known of many fish that breed in less than
optimal conditions. In my public aquarium
days, our indigenous ray tank was a horrid
and primitive thing, with barely functioning
undergravel filters and constant water
quality woes. Could we stop them breeding
in there? Could we heck. Every morning
we were netting out eggs and babies.
As for the claim that people are keeping
them successfully, I’d be inclined to leaf
through the dictionary and see if we’re
using the same definition of success. Is
mere survival success? I guess for some it
is. But is it success to have a fish in a tank
not even as wide as its own disc? In a
tank where to turn around is a chore? I’m
not sure we’d be reading from the same
page with such a claim. For me, success
would be seeing stingrays behaving as
they would in the wild.
shutterstock
Good intentions
In the hobby, for the best part, the stingray
phenomenon has been left well alone.
The collective of stingray keepers – there
are many stingray keepers – are a breed
apart from most ‘lay’ aquarists.
Nobody buys a stingray by accident or
on a whim – they’re too expensive for that.
Most stingray keepers do seem to have
good-sized tanks. Some have even set up
indoor pseudo ponds – large bodies of
water with three bricked and lined sides
and maybe a glass panel at the front.
There are more large tanks now than
there have ever been. I see images of folks
sharing their custom purchases, hulking
great lumps of glass on welded metal
stands. I see people actually researching
the fish before they buy them. They post on
social media, visit forums, watch videos.
It feels like evolution of the hobby. A
handful of aquarists who have grown fat
on nano tanks are pupating, emerging as
new creatures with fresh ideas. As nano
declines, the big tanks grow, in all senses.
I prefer to observe and reflect the
industry, rather than make proclamations
about it. And my observation is that the
stingray keepers seem to be sailing a
pretty good ship. With the ever-present
exceptions, they care and invest in their
fish, and in no half-hearted manner. The
fish are trophies, for sure. All dangerous
fish have a trophy quality about them, and
stingrays have the power to kill. But these
trophies are also pretty. And pricey.
That’s the real difference, I think. The
classic tankbusters were ‘throwaway’ fish.
Cheap. Disposable. A stingray is anything
but. Maybe they’re not tankbusters after
all. Maybe there’s something to be said
for being a trophy fish...
114 PRACTICAL FISHKEEPING
Guess the fish answer from page 30: Dwarf gourami, Thichogaster lalius