Here is a picture of my 30 us gallon setup.

I have a tetra filter on the back rated for a 30 gallon tank. I have been thinking about upgrading the filter in the future but I don't want to turn the tank into a whirlpool as well.
I have also been thinking about getting a canister filter but I really don't know much about them. Either way I'm going to keep my current filter and just do the normal 20% water changes ever 3 days.
What should be my next step to make sure he is happy and healthy other than getting the snail colony producing enough snails to keep him busy hunting. I have tried everything to get them going short of diming the lights and playing berry white. They are trumpet snails (the only ones I can find) and I'm aware that they are not ideal, but they will have to do until I can find common pond snails.
Another question is, when he has been feed he tends to hide under the filter or behind some wood. Is this normal or a sign of over feeding?
Thanks for your feedback.