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Re: Problems with my tank fish dieing

Robert Marshall wrote:
> I am using clay and sand as a substrate.  My plants 
> are doing very well.  So well I have to remove one because it was
> growing out of my tank.  I removed it my water became cloudy and the
> next day half of my fish died - including a recently hatch group of
> Apistogramma cacatuoides still in a coconut.  I am using a fertilizer
> used in a water garden which is safe for fish and is (14-3-3).  Are 
> the fish dying from hydrogen sulphide because of the substrate?
Hi Rob,

I would suspect a release of ammonia when you disturbed the substrate.
The nitrate in the fertilizer can be reduced to ammonia in the substrate
where there is a lack of oxygen. If you had fertilizer in the clay, the
nitrates and ammonia would diffuse out quite slowly until disturbed.
Free ammonia in the water won't last long after that. 

I do not suspect H2S as the culprit. You may have used a little bit too
much 14-3-3. It can be used by aquatic pond plants in very high
concentrations. I've seen the fertilizer tablets designed for water lily
baskets and these are very large! I've used Jobe's sticks broken into
small pieces and these are not so concentrated and are slow release.
I've also used clay balls with a few granules of Osmocote inside them.

They other possibility is that disturbing the substrate released enough
material that consumed the free oxygen in the tank. This is much more
likely in a substrate with an excessive amount of decomposing organic
material, such as compost or manure, in it. I would not expect this with
clay and sand.