I am looking for thin layer as well, don't want too much hassle of cleaning but don't want bare bottom tank as well.
Is it for the flowerhorn? With a thin layer he should keep it pretty clean with all the digging.
I personally never gravel vac since my substrate is thin. With persistent activity from pim cats, cichlids, or the barbs the whole sandbed is rearranged once a week it seems.

