When I first set up this aquarium I immediately had a problem with a brown algae like substance growing on everything. In fact, I had the same problem with the 30 gallon I set up just prior to this one. This outbreak is not brown algae but diatoms.

I believe my diatom outbreak is due to 2 reasons. First, the river rocks I used came directly from my yard. Even though I cleaned them well, they still have a large about of silica in them, which diatoms feed on. Unlike rocks i could have bought at the store, these don't have any protective coatings or specially chosen to not have silica in them. Second, I kept the original 50/50 Actinic bulbs. Although good for a marine tank (and the blue tint looks nice), they don't do much for plants and seem to encourage the growth of diatoms.

My Gold Gourami seems to enjoy eating the diatoms off every surface of the aquarium. In fact he did a pretty good job of keeping up with the growth when he was in the 30 gallon tank. So much so that I didn't feed him at all for weeks and weeks. For the 80 gallon I purchased two Otocinclus Catfish which will also eat the diatoms. None of them have been able to keep up with the diatom growth in the 80 gallon. I've been using a magnetic glass scraper to clean the glass, hopefully the fish will take care of the rest over time. Since replacing the Actinic bulbs with more natural sunlight producing bulbs, the diatom growth as seemed to stopped or slow down significantly.

Last week i decided I couldn't leave well enough alone and cleaned out the canister filter. I was very careful to wring out the foam pads using only aquarium water as to not kill of the bacteria with chlorinated water. i put the whole mess back together and turned it back on. Within a day or two I had a tank full of green water. This was clearly a algae bloom. My ammonia, nitride and nitrate tests all show good results and the fish are doing fine. When I cleaned the filter I didn't put the purigen back in so the live plants would get more nutrients. This most likely has allowed the algae to prosper as well. My test kid didn't include tests for stuff like phosphates so I can only assume.

I really really hate it when I have to buy some sort of new hardware but it looks like the best solution to this problem is a UV sterilizer. UV light will kill single celled creatures like algae by damaging the DNA if they are exposed to the UV light long enough. I decided to go with the 18 Watt Turbo-Twist 6X UV Sterilizer which cost about $150. UV light will destroy all single celled critters, including viruses and good bacteria. Therefore it's only recommended to run when you have a problem.

I'm still waiting for the UV sterilizer to arrive. In the mean time I've done a 60% water change, which has helped quite a bit. The live plants are still pretty new, it might take a while for them to get established and start using up the nutrients in the water