I would add a few reinforcements. Water rock and all, 180g weighs close to 3k lbs. Im in the same position. i have a 125g im rebuilding the stand on to allow for a 55g sump. If the construction is Peer and Beem, it really depends on how close you are to a Peer. If you are within 5 ft of a peer, it shouldnt matter if the under floor supports are at least 2x10's. If more than 5 feet, or the under floor supports are only say 2x6's I'd make a few reinforcements.