My gf gave me her old tank so Im going to get it started. I havent had a nice planted tank since my 29 cracked..... thats another story.... Anyways, the only filter I have is an Aquaclear 30, is this too big for the tank? Can I just put a plastic piece to disperse and smooth out the turbulence? Or should I get a little filter rated for 5-10 gal? Also are Corydoras suitable nano fish? I believe the LFS has "Panda" and "dwarf" varieties. How many could I put in here?