Freshwater

Figure 8-12:
Koi get too
big for an
aquarium,
but are
great for
ponds.
Although many fish such as the guppy can live in cooler waters, we will focus
on other non-tropical varieties. In today’s market, for example, many beautiful
varieties of goldfish will fascinate and amaze you. These are not your
garden-variety feeder goldfish found at carnivals!
Koi
Chapter 8: Finding Your Species
Koi (Cyprinus carpio) is a highly colored omnivorous pond fish that is related
to goldfish (Figure 8-12). Because of its large size at maturity (up to 3 feet in
length), it is unsuitable for an indoor aquarium. The torpedo-shaped koi
requires a good filtration system and many plants, which it uses for food and
shade. Champion varieties can be very expensive, but have outstanding color
and beauty.
Koi do not do well in acidic water, so their pH needs to be kept between
7.0–9.0. They must be kept in ponds that allow them to remain cool throughout
the year.
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