For some reason, whenever they get startled, my p's feel the need to swim behind the intake of the power filter. Neither of them are small enough to really fit behind it, so it flexes out so they can fit. once i noticed that one of the p's eyes was kind of puffy and i think it is from trying to squeeze behind the filter. is there anything i can do to discourage them from doing this? is it possible they think it is providing some cover and want to be behind it? one of my main problems with them is that they are too big to hide behind plastic plants or anything, so they're usually just out in the open.