Really can't tell you as it would depend more on your stand than anything. IMO, getting macro in there is much more important than more rocks, if you have 1lbs per gallon in your DT, and a deep sand bed. Any chance at extra room can give you the ability to add more goodies, or get them out of your DT. I have the smallest aqueon sump that they sell (didn't have time to make one due to work), but have my heater, fuge w/ cheato and ~3k pods, and a uv sterilizer in mine. I had my skimmer in there, but when I upgraded my tank my new return took up to much room so it went back to HOB. Really miss having it in the sump.