So, I have a 20g tank where I have a upside down catfish with a lot of acceptable hiding places, but he took to my filter underneath it and around the sides. The past few days he disappeared for hours at a time and I thought he took to a new hiding place, but then I was watching the tank checking everything and I notice him swim out of the bottom of my filter and when he was done swimming around and eating, he swam back into it! Does anybody else's do this? I have an Tetra Aquaculture Aqu-tech Power Filter. Is this something I should worry about for him? If it is will it stress him out too much to block his hiding spot?