I have a 20G long that I set up as a frag tank out of necessity when all my zoas started dying. I don't have any rock in it and don't really want to put any in so I want to set a tank, maybe 10G, next to it and fill it with live rock to use to filter the 20G. First question is does that make sense and if so how do I get the water from one to the other and back again without drilling any holes and without having to worry about a malfunction overflowing either one? I've tried to do a little research and have found there is an overflow box that may be used in this situation but I'm not clear on how to implement that or if that is the only solution. Thanks again for any help or advice.