Hello, I have a 50 gallon tank that is not in use (acrylic) and I wanted to get a mantis shrimp. I'm only going to have about 30-40 pounds of live rock and have maybe 5-7 inches of sand. Is that ok? I know that after 3 inches of sand, the sand because dangerous because of the nitrite, but can someone back me up on this? And also, anyone suggest a certain type of mantis? like a peacock or something? Thanks