I did a BB experiment with my 40g SPS tank. I don't think it went so well. My NO3 and PO4 levels were no better than with a SSB. I'm now starting vodka dosing. I'm thinking of adding a sandbed for some gobies I want to get. I'm not sure what sand to get though. I have a lot of flow. I have a vortech mp20 and koralia 4 plus my return. Carib Sea had some sand that was 1.0-2.0mm. I thought this would be a good size.