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Fry Filter Help


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A sponge filter is commonly used for raising fry because it has a very slow, gentle flow that will not trap baby fish or break backs or deform fins. They are also very versitile and can be "upgraded" in steps until the fry are using a standard filter.

This is one of the best sources for sponge filters that I have found:


A sponge filter should be set up in a tank as soon as the eggs are laid. Cleaning ALL the water and rinsing the eggs gently with clean treated water will remove the majority of the waste that is left behind in a spawning - starting the hatching tank out in good water. SEt up one or two (or three depending on tank size) sponge filters going with air stones. The action of the air bubbling up through the center of the sponge will draw water in through the sponge and out the top. Your beneficial bacteria will set up shop on the miles of surface area of the sponge. They work to process the ammonia/nitrite of the tank as the water flows through.

A cycled sponge running from the day of spawning should be enough to keep your water parameters in good enough shape that you will not have to change any water for about 7 days post hatch. This will protect the babies.

I also have designed an air bubbler system that will draw water out through the sponge and "syphon" the tank with no harm to the fry. It takes a while but you will never suck up a fry or damage a back.

As the fry grow, you will need to get more gph - so I usually plumb in a small filter hose to the sponge - sucking the water in through the sponge and returning it in a gentle outflow at the top of the tank. This power filter drawing through the sponge is capable of handling waste for a couple more weeks and a few more culls.

Finally, you can use the sponge to cover the intake grate of a regular filter. It protects the fry from being suctioned to the filter intake grate, adds more biological filter surface area for the BB and is easy to squeeze out and clean. I have removed the sponges, finally, when the fry are about 1 inch in length - strong enough for the currents and suction of an Emperor 400 or whatever I am using on the tank.

A nicely seasoned sponge filter is also a boon when traveling with fish. A simple battery powered airbubbler can run a sponge filter for hours - filtering and keeping your fish safe while you are on the road for several days. I try to keep seasoned sponges available at all times - you never know when you might want one. They are cheap enough to cut up into pieces to stuff in a filter, cut to fit an intake or to discard when they finally get too clogged to squeeze out right. They are a nice addition to your fish "stuff" casche.


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