I have a 10 gallon tank with 2 reg wag platies, 2 black mollies, 2 scissortail rasbora and a upside down catfish. The catfish doesn't move. He stays under the filter. I moved it enough to get him away from it because I was afraid he was stuck to it. As soon as I moved it away from him he darted to the other side of the tank and hide in the plants. No sooner did I get the filter back in it's place and the lid back on the tank he was back under the filter. I'm afraid he's not even moving to eat. Any ideas on why he's staying under the filter? If I can do anything for him?
not unusual to see a wriggling black ball of fighting catfish 
I found him there for the second time this morning and had to move the filter for him to get out from behind it and back under it.
especially when mine is a bit tubby round the middle
i was thinking about doing a google for "atkins for fish" 
They aren't nigriventis to be fair, which I assume yours is. They are much happier in groups. You need a bigger tank.
Try putting in some more hidey holes. Say a nice fake tree root thing or some such and put the filter in a different corner so the new hidey hole is where the filter used to be. And they really can squeeze into tiny spaces. It's highly unlikely he'll get himself stuck, even if he looks it. Best option really is a bigger tank.
* I just can't get one but so large...I live in an apartment on the top floor with only steps. But...as suggested, giving away or finding new homes for any of my fish is out of the question. I'm stubborn and have grown to love them already
So he's just going to have to stay an only child until I come up with the funds for a bigger tank, or another tank...Or Santa comes and brings me one! I just hope he is eating...I can only assume he is since he's still alive....But it still appears as if all the food I put in for him is still there after each feeding *AM before work at 7, and PM around 7 or 8* As for now, it's around time for dinner time and there is still his food there from this morning. He's getting along ok with the other fish, they swim over to the filter and hang out and none of them fight or bother each other. We'll see....