I am wanting to downgrade to a "holding system" for the next 3-5 years. I am going with a 80 gallon frag tank, a 20 gallon (small tank), and a 50 gallon sump. Water would drain from the frag tank into the small tank, then into the sump. I would like to keep rock out of the frag tank and originally was going to fill the small tank with rock and put the skimmer in the sump. I'm now thinking I want to put the sump under the frag tank to save space but am worried about accessing the skimmer. Would it make more sense to put the skimmer in the small tank and the rock in the sump? I figure most of the detritus will settle in the small tank and accessing the skimmer would be much easier here. Thoughts?