I have 6 multies in a 20 gallon long with over 100 shells that cover the floor of the tank. I introduced the 6 of them to the tank yesterday but now can only count up to 5. They're very shy but at this point where 4 of them are always hovering around and the fifth one being the smallest of all still making appearances here and there, where could the 6th one be? I also wonder if maybe the tank is too large to feed them all since they still get spooked when I come near the tank and hide instead of coming out to eat. I'm especially concerned about feeding the smallest one since he is hard to spot and always gets lost in some shell or other. I think I have too many shells for this tank with the number of fish I started out with! What do I do?