I haven't been able to keep any slope in my 120 with BDBS. It may be because I have high flow inside the tank, but I'm guessing it's just because its sand. I asked about this before and did hear one response that made sense. A guy took stiff black plastic sheets and created "retaining walls" that helped him maintain slope. FWIW I'm changing to a 240. Bought 500lbs of BDBS last weekend. I'm just going to start out with it level. They don't have as many grit sizes as they used to have. Basically a coarser grit combo or a finer grit combo. I got the coarser, and wondered for a moment if it would hold a slope, but starting level as previously mentioned. Good luck!