In my 125L I've got 6 corys, 6 (so far) kuhlis, 10 MTS, amano and cherry shrimp as my "clean up crew" (along with the other stuff in my sig) and I've given up "gravel" vaccing the sand.
It's quite well planted. I don't have problems with the sand looking "dirty".
I did for a short time get some strata of the sand going blue/black (cyanobac?) but once I planted eloda (anti-bacterial properties) and added the MTS it cleared right up and the sand is all nice and pale sandy coloured now.
I give the sand a quick "stir" with my fingers (being careful not to go too close to the plants) when I do water changes, pretty much only to loosen it as it does compact.