I am moving, and instead of tearing down and reassembling my 90 gallon reef, I am going to set up a 125 gallon, using as much from the 90 as I can, to make the transition easier (and appease my desire for a larger tank). I found a used tank, and it has three holes (with bulkheads) along the back side of the tank toward the top of the glass. I am wondering what I should do with these, and how to plumb them for a sump. In my mind I see a gravity feed to a sump, a return line, and a 3rd "mystery hole." Help me out please!
Thanks in advance
Thanks in advance