i have a 15 gal hex, and was planning to buy a larger tank when i get enough cash. I thought a prizm might be good because i can just reuse it in the larger tank. I was wondering if i needed an extra filter if i bought the prizm, the guy in the store said i wouldnt need one..... seemed kinda strange for me, I have an anomie, mushroom rock, a cleaner shrimp, a electric blue damsel, a clown, a scarlet reef hermit, and a turbo snail. I was wondering if i still need a filter, im using a fuval 2plus, i know its not really a saltwater type of filter but im just reusing it because i feel guilty blowing 30 bucks on a filter i only used for 4 months on my turtle tank =. So yeah.... would i still need an extra filter, i have no extra room if i get that prizm skimmer, PLUS!!! I NEED THIS!!! I HAVE 71/2x 21/2 inch wide space on my hex, WOULD I BE ABLE TO FIT THE PRIZM IN?!?!?!? can u give me the measurements for skimmer?thanks