In the 10g I mentioned earlier, with play sand substrate, I initially had no filter. Lots of plants, and I mean lots, and just a group of 9 Boraras brigittae which are very tiny fish. The tank never cleared, and I mean after several months. I added a small sponge filter and it cleared within a day. This in my view was not the sand, just the biology.
However, the sand took endless rinsings and it never did run "clear" the way gravel will. But in the tank it should settle out. Be very careful with filters; sand is very easily drawn into filters and will destroy them. A sponge will clog but that is easily fixed by rinsing the sponge. Personally I would never use sand in a tank with any other filtration. And from my experiences to date, I am much less inclined now to try sand in another tank than I was when I set this one up.