I know you've been back and forth with sand in the past but I'm going to speculate that if you add sand and give it some time you'll find an uptick in your growth rate. This is not to say that you can't have great growth and color in a BB tank but that in your present case it may help. The substrate could theoretically allow for increased zooplankton in the water column and thereby food for the corals. Some substrate will also provide surface area for the precipitate you are reporting having problems with in your pumps. If you notice some clumping you can stir the sand manually and replace a little with your water changes a la Steve Weast.
On the one hand I like substrate because it reflects some light and provides a "finish" to the tank and on the other I hate it because it really dictates my flow pattern with a higher flow tank. But in the end it's just a few hours of work to remove it if you really hate it. And it gets more fun every time you do it
(I've now been back and forth from SSB to BB 4 times in the last 2 years).