The other advice on changing water in big tanks is use big diamator hoses. When I had my 250 fw
set up, I could drain and refill in 15 min. Using a 1inch hose to empty and a 2200gph pump to fill. Problem with that is, no room for errors. So just be careful. If a 1inch hose misses its mark, you have a big clean up. As far as going poor from filling tank with coral, I can't stop. I found ebay has very cheap coral auctions. I can pick them up locally and they are the rare and unique. I won't tell you the name because they are mine. all mine. Stay away from my precious!