100lbs of base. Thinking I might need one big premium in there and stack the one in the corner on top. I put 3 softball sized ones in the sump. the 3 rocks on the corners are pretty good caves and the rest is more like tunnels from stacking. after 7 days, only a little ammonia rise. Pulled out 10 gallons of water, put the sand in, then replaced with fresh salt water. After it cleared this morning, I aquascpaed some and did another 4 gallon change. will leave it like this through the holidays and monitor the levels. Lots of colorful sponges, red, yellow, white, blue. 2 brittles are crawling around. Might get more for the sump.Looks great. Is this the premium or base?