I'm going to be setting up a tank about the same size as a 15 long. It's got overflows and was wondering if I'm going to be loosing fish in the overflows all the time. I know there are a number of you guys running large tanks with overflows and small fish but I'm a little concerned since this tank is so small. Would I be better off stocking just a couple rams or something instead of a school of small fish like cards?
I cut a long piece of window screening and attached it to the front of the overflow gate, I adjusted the holes of the overflow to the largest ones(not sure if your overflow allows this) to allow the most water flow as the window screening blocks a considerate amount of flow
When I tried a sump and over flow I lost several Rummy Nose Tetra. I tried covering the edge of the over flow with net but then plant leaves would block flow to the over flow. I decided out was silly for a planted tank, sold it and put my canister back on.
I have ~1200gph flowing over my 13" wide glass overflow, water rises about a 1/4" ontop the glass. Sort of a stray baby pleco, who can find their way out, all the fish are fine with it as long as you cover your plumbing with strainers.
I have lost fish as thick as medium sized corydoras through the skimmer teeth. I keep the drain covered with a sponge to catch debris so fish don't go to the sump until I pull out the drain tube. I used to be able to fish out the overflow box but cannot do it with the eshopps box. The drain goes to water in the sump so any fish that go overboard are just fine. A black neon tetra fry actually grew up in the sump but the usual occupants are small platies, black neon adults and otos.
Since my fish are attracted to the delicious brown goo in the box and debris hanging on the skimmer teeth maybe keeping the area clean and boring would keep them away? Stop the pump when feeding so food doesn't go overboard?
As long as the drain dumps into water, not a sock or filter media, any stray fish will be just fine. The water in the sump where the drain dumps isn't turbulent enough to bother fish.