SiRWesDragon said:
Never have problems with diatoms cause I have a powerhead circulating the water all the time. Diatoms cant stick with water circulating. And also have 2 plecos eating all bio film. And 3 canister filters. No problems.
Not sure if that is really true, I had diatoms on my glass for a while in a new tank, and there was plenty of flow everywhere in the tank. They even grew on the glass directly across from my filter's outlet, which obviously had more current than the rest of the tank.
The three canister filters are probably the main reason you don't get diatoms- especially if any of them have UV. And the plecos will take care diatoms before they can even form in my experience. Also, if your tank is well-established, there probably aren't any silicates left in the water to promote the growth of diatoms anyway.
Don't mean to argue, but I don't think the claim that more flow -> no diatoms is always true.
edit: also, to stay on topic, I doubt that you will be able to find anything white that won't have some silicates which will dissolve and promote diatom growth, especially if you run with a PH less than 7. I would think that an acidic PH would just keep dissolving more and more silicates from the sand, and you would keep having problems with diatoms. You could try raising your PH with some crushed coral or something like that; since I put a bit if crushed coral in my 20 it hasn't had much of a problem with diatoms like it did at the beginning.
You could try soaking whatever you end up getting in some fairly acidic water for a few days, and keep changing the water out, that may get rid of some of the silicates that might be left over when you just rinse it.