Energy is finite - especially with fry
by Terry Ranson
From Vol. 1, No. 10 The Newsletter of The Tri-State Aquarium Society September 1999
Aquarticles
There are many factors which affect the growth of fish fry. Most of these are known and
addressed by aquarists. We know the importance of feeding live foods to ensure proper
nutrition, and of performing frequent water changes.
However, energy conservation is also important when it comes to getting fry to grow as
quickly as possible.
I once observed two aquariums containing young Festivums, Cichlasoma festivum,
and noticed a large disparity in size in the fry, even though they were all from the same
hatch. Both tanks, which were directly beside one another, were the same size, and the fry
were fed the same food. Yet the fry in one tank were noticeably larger. The only
difference in the two aquariums was that the tank with the smaller fry had a strong
current coming from the power filter. Energy is finite- especially with fry. They were
forced to expend much more energy simply to swim. The second tank was filtered in a way
which did not result in a strong current. The fry used little energy in swimming, and grew
more quickly.
I have a home-made aquarium with a built-in filter which was originally constructed for
keeping male bettas. I've since taken the dividers out, and use the tank to raise fry.
This tank holds about seven gallons. I once raised a batch of black molly fry, dividing
them evenly between the seven-gallon tank and a standard 20-gallon long. The fry in the
smaller tank grew at approximately twice the rate. The fry in the 20-gallon had to use a
large portion of their energy to feed in the larger aquarium. The fry in the smaller tank
used that same energy to grow.
I realize this goes against the traditional aquarist's philosophy of, "The bigger
the tank, the faster they'll grow." However, I have duplicated these results with
several species. Of course, when using smaller containers, common sense should be used.
With small tanks, you need to do more frequent water changes. When they become crowded,
place fry in larger quarters.
Energy is finite. Fish use energy in whatever way they must. If you want them to grow
as quickly as possible, make certain they don't expend energy needlessly.
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