Managing Fish Wastes
The most important rule in fish nutrition is to avoid overfeeding.
Overfeeding is a waste of expensive feed. It also
results in water pollution, low dissolved oxygen levels,
increased biological oxygen demand, and increased bacterial
loads. Usually, fish should be fed only the amount of
feed that they can consume quickly (less than 25 minutes).
Many growers use floating (extruded) feeds in order to
observe feeding activity and to help judge if more or less
feed should be fed.
Even with careful management, some feed ends up as
waste. For example, out of 100 units of feed fed to fish,
typically about 10 units of feed are uneaten (wasted) and 10
units of solid and 30 units of liquid waste (50% total
wastes) are produced by fish. Of the remaining feed, about
25% is used for growth and another 25% is used for metabolism
(heat energy for life processes). These numbers may
vary greatly with species, sizes, activity, water temperature,
and other environmental conditions