I had two ac70's and a magnum 350 on my 150, you can get a used magnum 350 for about $30 or $40 bucks as well as ac 70's. I figure you could do two 350's, two ac 70s, or one of each and be fine, I would recommend one canister for the added biofiltration but ac 70s hold a decent amount of media as well. I too am a broke college student so I buy used, you could do a diy overhead filter or sump with two fp 500's (500gph) 10 bucks shipped on ebay. http://www.ebay.com/itm/SMARTPOND-R...aultDomain_0&hash=item2a1429996f#ht_561wt_905