Sponge filter are the only filter i use for bettas, i have a 70-80 gallon pump, for all 7 of my bettas(got 2 yesterday :) ) gang valve them all to desired rate, or you can make them out of hair curlers, or make them from soda bottles, though if you can wait go on ebay and get the cheapies, usally china made :( but can get for cheap. Also spong filters isnt just for small tanks, i run one in all my tanks with canister and HOB. I have a 125, 75, sevral 20 Long planteds and a soon to be 55. my lfs has a cichlid tank, 90 gallon with 3 giant ones as sole filtration, creates the current they need aswell. I am !0000 % in agree with the sponge. Old school for a new genertation.