# Diatoms in established tank



## veryzer (Oct 25, 2009)

Most of what I've read concerning diatoms state that it's common in new setups due to ammonia spikes. However, I have an established tank that had a diatom outbreak about one month ago after being set up at least three months. I've been waiting for things to settle down but no luck. I haven't had NH3 issues. The problem started the day after changing half my filter media. Any ideas would be appreciated.


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## darryfish (Feb 15, 2010)

Well, if it happens after a change of filter media, it could be due to an ammonia spike due to a mini-cycle (as the new media is growing its coat of bacteria). But I'm not sure how likely I would say that is... IME with established tanks, there is enough bacteria culture, not only in the filter media but in filter tubes, in the gravel, on the plants, etc. so that I don't experience mini-cycles when changing filter media--even if I change all of the media at once.


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## veryzer (Oct 25, 2009)

That's exactly what I thought, which is why I'm mystified. I'd think even if it were a mini-cycle the tank would've reached equilibrium by now. From the lack of answers I'd say everyone else must be just as stumped.

Thanks for the reply.


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## svenhipsta (Dec 16, 2009)

veryzer said:


> Most of what I've read concerning diatoms state that it's common in new setups due to ammonia spikes. However, I have an established tank that had a diatom outbreak about one month ago after being set up at least three months. I've been waiting for things to settle down but no luck. I haven't had NH3 issues. The problem started the day after changing half my filter media. Any ideas would be appreciated.


Your filter media was converting ammonia to nitrites and then nitrites to nitrates. guessing you have your tank well stocked with animals. you now have probably less than half the bacteria you once did trying to keep up.

next time think twice before messing with your filter media?


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