absolutely check your overflow if you have one. I used to have a feisty fire fish that I would have to rescue from my over flow about once per week. Luckily I have a foam prefilter in the bottom of the over flow so he would always be contently swimming around at the bottom of the over flow in about an inch of water. If you have no such prefilter check you plumbing all the way down to your sump. I used to take the foam filter out and let him wash down into my sump and then net him there and return him to the main tank. I think the little booger learned to like the ride and did it on purpose, LOL.
