Basically i moved my betta to a 5 gallon because his fin got ripped either attacked by tankmates, self inflicted or because the filter was too strong for him, i don't know. I bought this new filter, it says for delicate tropical fish but it seems too strong for the betta as when he passes by there, he seems to have difficulties swimming and his tail is getting sucked up. So question is can i put a sponge? And do you think he'll be happier alone in a 5 gallon or back in the 21 gallon with tankmates? Thanks!
Also guys, HAPPY NEW YEAR 2013, Mayans are dead, we are alive :D