Plain and simple... Both work, and both sand and bb comes with challenges. I personally feel, that with an all out sps system, bb offers the corals tons of random, non-direct flow, which most sandbeds would not appreciate. Yes you can use heavier grade substrate to allow for good flow, but again, sps love flow. My system is bb, and all my pumps, including return, run at 20-30%, and in this situation, most sandbeds would be disturbed. But here's what I like, 2 times per day, for 30 minutes, I up my return to 70%, and power heads to 100%. Now, in this nutrient export mode as I call it, there would be no chance for any substrate, except maybe CC to remain settled.
As far as bacteria homing, I will simply say that sand is not the only surface area where bacteria homes. Overflow, plastics, glass, pipes, rock, and biomedia all allow for this homing, so sand from that standpoint is unnecessary. True, sand offers stabilization of ph, as well as mineral buffering. If I ran a mixed reef, my strategy would be different, and likely sand would be in play. To each there own, I have run both systems over the last 17 years, but everytime I have removed a sandbed, I swear I will never go back, but alas, I have, I am a sucker for the look of a sandbed, lol.
Happy Reefing to all!!!
