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Re: Disaster, lost all 13 koi last year and colony of frogs!

Subject: Re: Disaster, lost all 13 koi last year and colony of frogs!
by electrogear on 17/4/2011 8:07:59

It does sound like the plants were a contributing factor. When plant matter breaks down this produces ammonia, adding to the bioload in your pond. The oxygen exchange is also stifled when the surface is covered with plants, plus as previously mentioned oxygen will be removed over night. I'd say this change in water chemistry and the fact you had no filtration running which (with a decent population of aerobic bacteria) would have coped with the increase in bioload from the plant matter. To a certain extent the mud would have acted as a natural filter but it's a poor filter in an artificial pond with a larger concentration of fish than you would get in the wild, this is why people tend to use an artificial filter. I can only really echo what has previously been said about the long term build up over the course of the year, coupled with this change in the nitrogen cycle has caused loss of oxygen and/or an increase in ammonia.