Originally Posted by okapizebra
Diatoms are usually in a tank until they have eaten all the excess silicates in the tank.
Exactly. If you keep getting diatoms, then something is supplying that tank with silica.
Here's an interesting article about diatoms. It's written for saltwater tanks, but the basic concepts apply to freshwater. http://www.aquaticcommunity.com/aqua...ad.php?t=60144