I just put a new bubble wall in my 37 gallon - this one suctions to the base of the wall almost the whole length of the tank...lots of teeny bubbles and one of my corycats has decided surfing is his sport and he keeps riding the bubbles all the way along near the surface, when they end he turns around and does it over again...for 10 minutes since I first noticed it and he isn't stopping! Some of the new bloodfin tetras think it's fun and keep trying to school with him too....good investment I guess!