Description
This article is from the Beginning
Fishkeeping FAQ, by Thomas Narten with numerous contributions
by others.
55 Purpose of Water Changes
The solution to pollution is dilution; water changes replace a portion
of ``dirty'' water with an equal portion of clean water, effectively
diluting the concentrations of undesirable substances in your tank. In
an established tank, nitrate is the primary toxin that builds up.
Regular water changes are the cheapest, safest and most effective way
of keeping nitrate concentrations at reasonable levels. During the
tank cycling phase, however, ammonia or nitrite may be the substances
that need to be diluted and removed. Likewise, if medications have
been added to your tank, they may need to be removed after they've
served their primary purpose.
The effectiveness of water changes is determined by two factors: their
frequency and the percentage of water that is replaced. The more often
water is replaced, or the greater the quantity of replaced water at a
change determines overall effectiveness.
The benefits of water changes must be balanced by the stress caused by
a sudden change of your tank's water chemistry. If tank water has
similar pH, GH and KH as tap water, changing 50% (or more) of the
water at one time will not affect fish. On the other hand, if your
tank's pH is (for example) 6.3, while your replacement water has a pH
of 7.5, replacing 50% of the water all at once will change the pH of
your tank significantly (possibly more than 50% depending on buffering
factors), which will stress your fish, possibly enough to kill them.
Because water changes are the first line of defense in dealing with
problems such as disease, you want to be able to do large, frequent
partial water changes during emergency periods. Consequently, you want
your tank's water chemistry to closely match that of your replacement
water. That way, you always have the option of performing large water
changes on short notice. Note that this is the way tanks start out;
when you initially set up your tank, the water is the same as that
from your tap. Over time, however, the tank's water chemistry may
``drift'' relative to tap water due to acidification from the nitrogen
cycle, the addition of chemical additives such as ``Ph-up'' or
``Ph-down'', the use of non-inert tank gravel (e.g. crushed coral or
sea shells), etc.
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aquaria, fish, acquarium, tank, fishkeeping
