It would probably be OK, but based on your signature, you may have other problems. You may want to really think about those horseshoe crabs. They will destroy a living sandbed and, as they get older they will be huge. A 45 gallon tank would not be enough room for 1 of those guys. They will also knock everything over in your tank. Also, a 45 is too small in most folks' opinions on this board for a tang. They need a lot of room to swim. Lack of space causes stress in tangs and is probably one of the primary causes of ick. These are just suggestions.