pretty soon ill be purchasing a used 250gal tank that includes stand, lights, and a wet/dry filter with bio balls.etc I have to start slow because of the cost of tank etc. so i defiantly want to DIY as much as possible i've had a 29gal freshwater for quite a time and the new tank size will defiantly allow saltwater so i need to start with a sump, what size tank should i use to make it? i obviously have my old 29gal and an extra 75gal laying around. but does it have to be that big? i want the tank to start FOWLR. any suggestions are greatly appreciated.