30 gallon tall with about 75-80 pounds of rockwork for them to mess around in. I'm a big fan of biodiversity, particularly in the case of inverts in a reef tank. All of my shrimp and other inverts serve different purposes in the system. At this point I've struck a harmonious balance. One thing to note is that you should monitor what is happening in your tank. If there is friction, then remove one of the elements. This message board is vital in helping determine compatability of tankmates. I feel that you can have a few shrimp in a reef tank without having overcrowding, if you've got a lot of rock. The fire shrimp is always out and active. The peppermints are small and stay hidden during the day. They do spawn and produce food for the tank also. The monkey shrimp is only visible at night most of the time.