>Aquaria can be successfully maintained without water changes or with very
>minimal ones. The main reason that we need to do water changes is because our
>'sound approach' means getting a tank, putting too many fish in it and creating
>a very unstable system. So, to help reduce this instability we add filters and
>do water changes and such. However, were we to create a balanced
>micro-ecosystem, with a reasonable biomass for the tank size, and utilize
>more natural nutrient cycling systems, the need for water changes would diminish
>or disappear. Read _Dynamic Aquaria_, Walter H. Adey and Karen Loveland, 1991,
>where such concepts are explained in detail. We shouldn't get all charged up
>and think that we're doing the 'right' thing and keeping our fish in a
>'natural' environment, because probably 99% of us are not, if even any of us
>are. Most of our aquariums are over-stocked, relative not to how many fish
>your filter can maintain, but relative to how many fish would be supported by
>whatever volume of water you are dealing with or how many fish would be found
>in your tank's area (m^2) in the natural environment. Your filtration system
>itself is probably unnatural. In noneutrophic ecosystems bacteria are not
>primarily responsible for nurtient recycling (ammonia and nitrite removal in an
>aquarium), algae and higher plants are. Certainly, fish can be successfully
>maintained in these unnatural systems, and the system can even look quite
>natural, but it is not. I am guilty of this, but I recognize that my aquariums
>are quite artificial in nature, even those designed to mimic a certain biotope.
>Many of us set out with the goal of re-creating nature, so we only put fish
>that co-occur together, and we use plants and decorations that are consistent
>with these fishes' environment. Then we put a filter on it and do our water
>changes and look at it feeling as if we have achieved what we set out to do:
>the fish have a nice looking (to us) home, and they exist in a 'natural'
>system. Surely, we have imitated nature, but replicated? What of the
>invertebrate fauna of this ecosystem? What if our ecostystem is influenced by
>tides or some other abiotic force? Do we ever consider these aspects? Even if
>we do consider them, do we bother to incorporate them into our design? If we
>want to 'replicate what it is nature is doing', then we'd best make sure that
>we truly understand what nature is doing, and what direction we need to head in
>to achieve this goal. Nature is much more than the correct pH, hardness,
>nutrient level (all what we define as 'good water conditions'), photoperiod, and
>diet.
That sounds good, but describes a dream. It is not possible to imitate nature in
aquaria. You can't have aquariums in your private home for just a pair of fish
than in aquaria. And it is not unnatural to add filters as natural water bodies
also have self cleaning effects. Is it not useful to combine fish which co-occur
just because they co-occur (they may live in different niches we can't imitate)
but useful to combine fishes which have the same requirements. If you put a
rainbowfish in an aquarium with South American plants it doesn't matter - just
the positive effects of plants in that aquarium are important. There may be purists
who have another opinion, but the biotope aquarium is an impossible dream.
That was just a short reply, there are many more arguments why we can't try
to imitate nature perfectly but should look for the best way to maintain and breed
our fish.
Harro