I have a new 100gal that is 5ftLx 18inWx 18.5inH and I have gotten a few different answers to filtration size. First I was told to get a 125gal wet dry, but then the same guy said that it would be better to get a 200gal wet dry for this size tank to handle any filtration problems he said the bigger the better, and at another shop I was told to go with a canister set up. I already have an idea that I will be around the $400.00 range or higher.