The Light Limited Plant Aquarium - Silicon Valley Aquarium Society

The Light Limited Plant Aquarium - Silicon Valley Aquarium Society

The Light g Limited Plant Aquarium q


• What is a “light limited planted aquarium”?

• Is Light the best management option for

controlling the rate of “weedy” growth?

• HHow does d light li ht affect ff t CO2 uptake tk and d demand d d

in plants?

• Nutrients?

The big 3

Light g

=> CO2 => nutrient

High light? ~40‐50 micromoles

Not much really

What is the goal for “Light Light limitation”? limitation ?

• Reduced energy

• Reduced initial cost

• Reduced labor

• Reduced water change


• Better environment for


• Nicer aesthetics

• Reduce environmental

effects of Aquarium


How can light management help me?

Light => CO2 demand=> nutrient demand

• 20-30 micromoles

• 40 40-60 60 micromoles i l

• 75-90 micromols.

•No weedy growth

•Can this same tank be done

with 2-3x more light?

•Yes, but is it wise

management advice? No

•Has CO2, but high fish load,

still fair low maintenance and

low in/output

•Easy Easy slower growing species


•High Hi h current, t clean l water


No CO2 used here

What is this gardening

“like”? Hydroponics y p

CO2 enrichment – Higher light use

• CO2 enrichment => less

demand for resources/

enzymes to acquire i CCarbon b

• More resources now

available to maximize light


• Gets the most out of the

lighting without much added


• Lower light intensity possible

compared to non CO2/Excel

efficienc efficiency

What types of methods are available?

• Low light intensity is the key to sustainable

approaches => Why?

• Non CO2/ CO2 enrichment?

• Dosing Seachem Excel

• Emergent Paludarium/DSM

• Sediment nutrients?

• Water column nutrients?

CO2 gas/Excel

Excellent option for smaller nano

aquariums i vs CO2 iin

many cases

CO2 issues

• More complicated and less stable

than aquarist assume

• Errors kill 95% fish in planted tanks

• Not just a CO2 issue, respiration is a

both O2 and CO2

• Good current => well mixed CO2

• High O2 both during the day and night

• Healthier fish and cleaner tank

So why do aquarist obsess over

nutrients the h ignore CO2 and d light? l h ?

• A good myth is hard to kill

• Not looking at the big picture

• Poor measurement of f CO2 and d light li h

• Not looking at the real root of the problem/s

• Often said to test the water/No3/PO4 etc…….

• Rarely ever test the light for PAR or good

critical measure of CO2


Adding CO2 and adding light

24 micromol 89micromol 250micromol

Same relationship for CO2 =>

How about nutrients?

Non limiting range

What is non limiting?

Nutrients? Same old thing again

Then why bother limiting nutrients if

the h light l h or CO2 are limiting? l


Drives CO2 uptake


Drives Nutrient uptake


Drives Plant growth

Using water

column “only”

ddosing i in i a pure

non CO2/no

excel aquarium, q ,

no soil

“Tom Barr”

non CO2


Don’t like

the name☺

Dosing is 2-4X

a month, no

testing, g, fish

feeding is more

labor. No water

changes for 2


Where is the risk if nutrients are so

“Bad”? Fear mongering(why not “high light”

Bad ? Fear mongering(why not high light

is “bad and causes algae”?)

Nutrient locations

• You have a choice about where to add the nutrients

Plants are opportunistic, pp , they y will go g after nutrients

in either location‐both water column and the


• Makes the most logical sense to add them in the

water column and the sediment => get more

stability out of each this way

Use Fertile Sediment(why?)‐easy!

Sediment(why?) easy!

• Worm castings

• Top soil

• Delta l clays, l natural l soils il

• River and stream loams

• Plain sand

• Amendments/Ferticicles

• Commercial brands, ADA aqua soil(clay)

Trade offs for water column and

sediment d

• Sediment • Water column

• Easy to do once set up • Good source of NO3

• Low maintenance

• Good safe source of NH4

for plant roots

• Easy to add but more


• Easy to test/monitor

• Good source of

ttannins/humics i /h i ffor fish fi h

• Hard to redo

• No mess

• Gets nutrients to plants

without roots, epiphytes

• Messy if not careful

• Cannot test/monitor easy

• Conclusion: use both

locations‐ adds

redundancy to your


Is this low tech?

Low light

Sediment ferts

Water column ferts

Good efficient filter

Good water flow

Good plant selection?

Water change requirements?

Did Liebig have it wrong?

• Need to include CO2 into the “nutrient nutrient

model” for aquatic submersed plants

• Need to also include light

• Now we have a holistic model to understand

and d predict di plant l growth h

Light is very stable, so maintaining a low

stable concentration is much easier with CO2/

any nutrient

RCS‐ another model organism for

sustainable breeding/algae cleaning for

Good selection of stock and

culling will yield very red

shrimps(generally 44-8$ 8$ each

for 1” retail)

planted aquariums

Poor breeding(bad inbreeding) lead to

poor environmental health(common

with shrimp breeders)

Fire shrimp, good breeding or not?

Good Good fish choices? There There are are many. many. What

sells, easy to care for/raise?

Good “crops”

(aquatic plants) • Bolbitus

Want to chose plants

th that t sell ll and d llook knice, i

easy to care for

• Needle leaf Java fern

• Anubias nana “petite” p

• Water sprite

• Moss of any sort

• Riccia

• Stem plant of the


• Emergent growth in

window terrariums

No CO2 issues now, high rates

of growth, g , excellent light g use

efficiency, export of waste

Refugium/utility or still maintain

nice aesthetics???


• Not much issue when the light is low low, since

algae are neither nutrient nor CO2 limited,

they are only light limited in aquariums aquariums……

• Slower algae growth and issues

• EEasier i to correct main i causes of f algae: l CO2


Algae eaters are more effective

• In low light aquariums, aquariums they are much better

able to control algae

• More effective per critter per unit area

• Algae grow slower=> more time to gnaw on

“ “young” ” algae l

• Shrimp are pretty effective

• Other fish(SAE’s etc) where shrimp cannot be


Filters and




•More efficient pumps

•Reduced heat

•Cheaper in the long run

every time

•Pays to get good

equipment upfront

A stepwise approach to management


• Low intensity but high quality light

• Rd Reduced dwater t changes h

• Good quality efficient pumps

• SSediment+ di t water t column l ffertilization tili ti

• Wise, plant, fish and critter selection

• CO2? Eith Either way‐ ttrade d off‐ ff more efficient ffi i t

use of light energy per unit growth

• Focus on all 3, 3 not just nutrients!!

Consider trying recued light

• Reduce the light and see how if affects growth

and CO2 and nutrients

• What is the minimum light intensity that will

grow corals nicely if the other parameters are

truly well cared for or independent/non


• If less is better, then this philosophy should

apply to each aspect of plant growth, and

aquarium keeping, not merely nutrients alone

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