Wow.. so I guess even you experts have these little issues too? I will try the "take a picture, and reduce it" trick and see how that looks. PinkRasbora, when you say stocked, do you mean with fish, or plants? I guess I can tell you everything: 15 gallon running 6 months with 6 full grown danios, 3 half grown fry. Filter: Penguin BioWheel 100. Heater. Kept at 76 degrees. 2 pieces of driftwood (one is grapevine, the other, I am not sure). Planted with anacharis, java fern, java moss, anubias, a wild onion, one cute little crypt, and a barclaya. Substrate fertilized with Aquarium Plant.com's fert tabs as needed. Under a 24" T-5 Coralife (suspected) 14 watt bulb. I know I need more light, and with that, I'll probably want CO2- those are my summer projects for after school. The tank is near a corner window where it does get additional light, but not directly. The water is faintly tea-colored from tannin from the grapevine driftwood; I didn't have a pot large enough to soak and boil it. It looked smaller than it really was in the store. =) I've started doing more little water changes more often during the week- little 2-3 gallon changes to possibly help with the tannins, and still do a big one once a week. Everything is growing well- the anacharis is always sending up new stems that I replant, and the cute little new crypt has doubled in size in only 5 days.
What I was finding is rarely BGA (which I scrub off with my fingers), some occasional GSA, and mostly just soft brown gunk or dust. it looks almost like the gunk that builds up in filters. It just looks like brown dust over the leaves, and brushes off in a small cloud like dust. The substrate is river pebbles, so there's no sand. I guess if I could clear out the tannins in the water it'd get rid of the dingy yellow shade on everything. The yellowy water and the purpley bulb appear to make the water look dim. I am sure they yellow/brown rocks don't help either. I'm considering changing to sand this summer as well. I bet if the water were clearer, it'd look a lot better, but there's little chance of that happening now that I have that driftwood "steeping".