yea... i kinda agree. if its up to a six inch fish, then should be a tank that should comfortably house a 6" gibby... i'd do it a bit longer than 3 times its length and about 4" wider than its total length footprint. as long as it can swim in an open space, have a hide or two and manourve around it'll be fine, as long as theres enough water in there to dilute the mess they create lol. a 125 wide would be good for a gibby