the overflows are generally built for reef tanks. they prevent a protein film from developing on a saltwater tank and allow for a sump.
squale said:I think a 150gallon is just too big for my house, I am putting it upstairs and I am afraid of the weight issue... besides, god forbid that tank ever sprung a leak, I would ruin the entire floor in the upstairs of my house. Plus my electric buill would probably go up considerably by having a tank that big in my home..