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Re: Losing corydoras :-(

Subject: Re: Losing corydoras :-(
by Fishlady on 2018/10/20 18:18:58

The majority of beneficial bacteria are housed in the filter so there is no need to avoid disturbing the gravel, in fact, if detritus builds up in the gravel anaerobic bacteria can thrive in the gravel and produce toxic hydrogen sulphide gas which is released into the water when the gravel is disturbed. If that is what has happened it may account for the deaths. There is a characteristic "bad egg" smell when hydrogen sulphide is present. There's an article here about this problem: http://www.fishyportal.com/cgi-bin/pub/diag?c=v&id=60

You need to syphon the gravel as part of your weekly water change to prevent a build-up of detritus and so also prevent a build-up of hydrogen sulphide gas.

As to filtration, if your current filter is controlling the ammonia and nitrite there is no need to upgrade to an external, but you can if you want to