Filters and Filtration
Even experienced hobbyists often misunderstand the mechanics of filtration. They
may assume clear water means good filtration, believing mechanical filtration is
effective filtration. In fact fish can live happily in murky waters, they can even
recycle their own faeces just like a rabbit. Some species, such as the Siamese Fighter,
can air-
The killer is ammonia and associated nitrite, excreted as soluble material exactly
equivalent to our urine. Being soluble it is invisible so apparently clear water
can be deadly. In the wild the huge ratio of water to fish dilutes this ammonia
so pollution is not a problem, but in the confines of the aquarium and many ponds,
ammonia can build. The chemical irritates the gills causing extra mucus to form
for protection. This reduces oxygen uptake and the fish are seen mouthing at the
surface (common sight in any goldfish bowl where it is wrongly assumed the problem
is lack of oxygen). It irritates the eyes and they swell (so called popeye). Marine
fish have to swallow the ammonia because of the osmosis effect in seawater and they
self-
Internal power filters are very good mechanical filters, whether powered, u/g or internal, but poor biological filters because of the low surface area of the filter medium. But it is biological filtration that is needed to remove the ammonia, because nitrobacter are required to do the job. These live on solid surfaces and convert the fish's soluble excreta to relatively safe nitrate.
To do this the bacteria need oxygenated water and a slow flow rate so the ammonia
(and nitrite) can be absorbed. Hence the best filter is the trickle (because it
has atmospheric oxygen) and slowly percolates over the bacteria, next is an external
flow filter, then the u/g system -
Less effective is the external power filter (but a better mechanical filter, of course...which the hobbyists wants but the fish doesn't need). The powered u/g is next and the powered internal filter the least effective, especially with small foam inserts. So do rely on lots of partial water changes to keep the water sweet and clear.
Experience shows one tank volume turnover per hour removes ammonia/nitrite in freshwater and twice per hour in seawater. Greater rates look good in advertising but may reduce ammonia removal (but increase mechanical cleaning).
Filtration categories are chemical, mechanical and biological but only the latter
is the life-
