Sudden bio overload.

How does a sudden bio-overload affect a Filter and how does this interim period adversely affect the Fauna in an Aquarium? How long does it take for a Filter to catchup?



Kev.

It all depends on the level of overload and the capacity of the filters to buffer against an overload.

I'll give a quick possible outcome....not that any of this is necessarily of any practical use in any one case study:

increased bio-load will increase the Biological Oxygen Demand.....that will affect the aerobic activity in the filters.
Some of the bacteria in the filter system working on nitrosofication may be facultative aerobes and so may start to work under anaerobic conditions: now that may just about keep them alive until oxygen levels rise again.

However, many of the bacteria will die through lack of osygen.

Then the increased bioload will increase substrates for the biological filters to work upon....and produce an increased levels of nitrites/nitous acid or nitrates/nitric acid, and may even start to work in reverse to produce ammonia from previously oxidised ammonia (not good).
The ammonia is toxic to the bacteria in the filter, and the increase in nitric and nitrous acid will cause a drop in pH...... that drop in pH will not only affect the fish but will affect the filter bacteria.

As the filter bacteria die, then they will add to the decay bioload and increase the Biological Oxygen Demand. etc etc and that is adding to the initial problem.

That is looking at one extremity. The reality depends on the level of the load and how mature and stable the filters are.

The bacteria involved in nitrosofication (ammonia to nitrite) will rapidly get a hold again in the tank; the nitrification bacteria (nitrite to nitrate) take a lot longer (several weeks) to re-establish and are the more sensitive in the commonly talked about bacteria in the filter.
The fuller maturity can take 6 to 9 months to be fully enoculated to cope with a fish tank.

If I had a biol-overload then I would instantly get my ammonia and nitrate removing resins, and do some water changes, and use a bottle of bacteria and then take things easy for while.

Ian