i disagree, if your planning to keep just the terror, then i say go for it. A GT will be comfortable in a 40gal for quite some time. GT's grow slowly and this will allow you time to either upgrade or find a better home for him. a 12 inch green terror is rare, the largest ones ive seen max out at about 8 to 10 inches or so. even if it were to grow to a foot, it would take a substantial amount of time. 75 gallons for one green terror seems a bit excessive.