I am on the SW side of this forum, but I now have a FW Tank question. What I have is a 125g SW tank with a corner overflow box, sump and skimmer, the sump has has a bubble trap and a chamber where the skimmer sits what I am getting is a SW 180g tank. What that means is my wifes son is wanting my SW 125g tank to make into a FW tank (which means I can't sell my 125 system and use the money for a larger skimmer as I will have to give the tank to him for free, lol *laughingc*crazysmil ). Anyway, I have never had a FW tank this big, just a 55g tank with a HOB filter, I told my wifes son the only thing that concerns me is the overflow box and the drilled tank with the sump. Where I am going with this is: Can he use the sump and skimmer in a fresh water tank. Any other advice you can give on this matter would be appreciated. My wifes son has my old 55g tank and wants to turn the 125g tank into an (sp) Oscar Tank.