A well planted tank will also help avoid those nasty anaerobic pockets; the roots will help bring O2
into the substrate. But that means REALLY well planted. Snails can also help as they will move thru the sand. I've sand in my planted 10g; at the deepest its about 3 inches, but I have a ton of plants running roots throughout it.
I wouldn't put the microbubble thingie in the sand; it will likely continue to kick sand into water column, which will get pulled into the filter and trash the impeller.
aka Cycling Guru and the Ich Slayer
*glares at Terry and QTOFFER*
Card carrying member of FTAS & GCAS.