Ok a friend just bought a load of live rock and has found 6 mantis shrimp. I am interested in keeping them but wanted to make sure if it is ok to keep more than one to a tank. I have a 10 gallon tank right now can upgrade later. how many would you recommend? They are 2 to 3 inches in size and a couple are really small. PLease let me know what you think. BTW i am new!! woohooo