By the way, you don't get to determine what corals you keep. It's a mantis tank. Anything he/she doesn't like, they'll simply drag back to their burrow to never be seen from again. Don't put anything too expensive.I've had a Purple Spot in a 10g Nuvo for 3 years. No skimmers, etc. Heater and pump. Water changes every two weeks or so. No way I would want to move a 40g tank multiple times in a few years. Water quality won't be an issue with regular water changes. I've kept both species and would recommend the Smithii. Be prepared how much they eat. They need a constant supply of crabs and snails.