The normal nitrifying bacteria die within a few minutes if without oxygen. That
means, that filters with no air which have a lot of debris inside have only few
time left to survive. However, in a normal aquarium so many of these "good"
bacteria are in the aquarium, the gravel, at the decoration, panes, plants...,
that the filter will be resettled with these bacteria within a few hours if
enough oxygen is provided. Not in a new decorated aquarium, with all new inside,
but in an aquarium which has run for at least four weeks already. Under these
circumstances the danger of a not running filter for the aquarium and the
nitrite/ammonia level is not very high if there is still enough oxygen in the
aquarium. However, is the tank is overcrowded, stopping the filter for an hour
or more may be dangerous for all fish.
Best regards
Harro Hieronimus, Solingen, Germany
harro.hieronimus at t-online.de
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No fish - no fun
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