Diatoms

[OliverArk]

Hi, I don't post very often, just read this forum a LOT, here is what I have going on, I have 2 tanks, a 40gal and my wife has a 20 gal with just 2 clowns, several snails and about 15lbs live rock and 15lbs sand. The tank is a little over a year old with no problems at all until about a month ago, the 40 almost 2 years old. The 20 is having a major diatom bloom. Both tanks get their top off water and water changes from an RO/DI system which I check all the time with a tds meter. The 40 gal is clean as can be. The lamps are within a month old. I have done a quick test for nitrates, I don't have anything to test for silicates. The nitrates show almost nothing. It just seems strange to have a problem with one tank and not the other. What other sources can silicates come from? Thanks for any info on other things to check.

[Ninong]

Silicate usually comes from the water and sometimes the R.O. membrane gets to the point where it's not filtering out silicates. In any case, there are many different forms that silicate can take in the aquarium and not all of them will show up on a standard silicate test kit.

I would suggest that you try using GFO (granular ferric oxide hydroxide). It removes phosphate and some forms of silicate. Poly-Bio-Marine's poly filter will also remove some forms of silicate. I think I would try the GFO first but if you happen to have any poly filters laying around, use one.

[yvr]

I think that quality of the salt used can cause diatom outbreaks. My local shop ran out of the TM salt that I had been using for years, so I switched to another brand and suffered a diatom outbreak soon after. After a bunch of water changes using my old brand of salt, it seems like i have been able to get things under control.

[OliverArk]

Thanks for the suggestions, I forgot about the poly filters, I do have one laying around here, I will give that a shot and pick up some GFO next time I am at the LFS. I'll let you know what happens.