I've got a 5 gallon tank that came without a filter and there really isn't a good way of adding one. The hood doesn't permit for me to use one of the filters that hangs onto the back lip of the aquarium.
Do I need to have a filter in the tank? Is there one that I can use?
Problem: What sort of sponge filter do I use? I got a Smallworld filter, but the air seems to go right through it pretty uselessly and the bubbles make a bit of a racket. I think if they were finer they wouldn't make so much noise... but what sort of filter do I use with the air pump system? >_<
Try using a gang valve to slow the flowdown? Mine was really bubbly too when I ran it full steam but once I turned the airflow down withe a gang valve it worked fine. That was with the Hagen Elite sponge filter. It may also be noted that box filters are the same thing, only stuffed with filter floss instead of sponge.