Clown Loaches do best when they're in big groups. This is what most people recommend. So if in your estimate a 90 gallont tank is good for ONE mature clown loach, then how big of tank would you need for a group of 6 or more? Also a standard 75 gallon tank and a standard 90 gallon tank have the same foot print. You've only inceased the height and not the area a larger clown loach needs.