~ Frequent Partial Water Changes ~
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Frequent Partial Water Changes
by Robert M. Fenner ~ Author of 'The Conscientious Marine
Copyright © 2004 www.wetwebmedia.com
Probably the most important aspect of maintenance a keeper
of an aquatic system can
do to optimize water quality and health of their charges is
to change some of the water
is a regular basis. This Section deals with the reasons
for, and some rules of thumb as
to how often, how much and how to make these changes.
There are several major benefits of frequent partial
water changes: Dilution of nutrient,
removal of particulate matter, reduction in microbial
populations and their metabolites.
Results anticipated are faster, more vigorous growth,
reduced algae growth, color and
It has been written in many fisheries, limnological and
hobbyist texts that along with
temperature and photoperiod, metabolite ("wastes")
build-up is one of the three most
important factors influencing the health, growth and
reproduction of livestock.
More specifically; in the trade, ammonia and other
nitrogenous wastes are recognized
as the number one killer of aquatic life in captive
conditions. Not to say that all the "stuff"
produced by the system's desirable life is toxic. Some
metabolites, like pheromones,
are actually known to have calming effects. Therefore the
concept of partial, not total
In doing these water changes we are interested in a
dilution-solution; that is, keeping
these so-called waste products at tolerable levels. There
are several ways this is other-
wise accomplished. Most common are some forms of biological
filtration and chemical
filtration like carbon and ion-exchange materials. The last
are useful but often labor
and money intensive. Moreover, these chemical filtrants do
remove desirable chemicals
As stated in so many previous Sections it is imperative
vital that as much extraneous
materials: foods, dirt from decor, material from the
immediate outside environment be
kept from getting in the system. What little does make its
way in should be removed
by netting/vacuuming, diluted or removed by making partial
Some potential pollution will probably be added to your
system in the way of food and
chemical additives/fertilizer. Even without over- or mis-
feeding and/or fertilizing, fresh-
water evaporation adds to a decided negative chemical effect
on an aquatic system.
This "Salton Sea Syndrome" occurs as water
evaporates leaving behind its' chemical
So enough of the reasoning for making water changes; onto
the nuts and bolts of how
to do them:
Depending on your pump/filter/circulation system,
stocking and feeding regimen et al.,
partial water changes about once a week to about once
a month are about right. More
frequent smaller amounts are better than infrequent
mega-changes, with one possible
exception. Some writers advocate an occasional massive
change (50% or more) as a
stop-gap measure to dilute metabolites, nitrates in
particular. I'd rather encourage you
to stick to regular, smaller volume changes; they're safer
and accomplish about the
Make a schedule/notebook for your system and keep track of
what you do and how it
works for you. Patterns will emerge and give you a guideline
for how frequent you
should change water.
Five to ten percent for larger systems and twice that
for smaller is generally sufficient.
The chemical/physical/biological shock from changing too
much too soon is to be
Though some marine authors state that water treatment
chemicals are unwarranted
with such frequent small percentage change, I'd encourage
you "to be safe, rather than
sorry", and treat to remove chlorine/choramine unless
you're preparing water a week
or more in advance of use.
However it is achieved, the part of the water and what's
dissolved in it are mainly to be
found at and in the bottom.
Solids are systematically removed from part, but never all
of the bottom of the tank and
possibly sump by using a "gravel vacuum". We don't
want to vent all the beneficial mi-
crobes along with the solids, so a plan is made to move the
decor and vacuum a half,
third, what have you, of the base in a given water change
New water is replaced with pre-mixed synthetic of similar
temperature and specific
Regardless of how well a system is designed and
constructed, there will always be
maintenance. Frequent partial water changes are one of the
best ways of ensuring
There are manufacturers who claim their products do away
with the need for frequent
partial water changes. Their products may well extend the
amount of time between
changing or ostensibly eliminate it, but at what economic
With the proper tools and materials, water changes are a
breeze. Water changing is
the cheapest, easiest, most sure method of diluting
wastes and replenishing buffering
capacity, "trace materials", while concurrently
cleaning the system of undesirable
solids and liquids.
Bauman, Edward. 1994. Water wisdom; as if changing a
little water will kill you.
Branscome, Lee. 1985. How to stop carrying those buckets of
water. FAMA 11/85.
Dow, Steve. 1986. Heavy water. TFH 5/86.
Fenner, Bob. 1999. Frequent partial water changes. FAMA
Hanford, Wilber L. 1969. A change of water. TFH 5/69.
Mowka, Edmund J. 1979. Water changes in the marine
aquarium; partial water
changes in the marine system are often neglected for
a variety of reasons. Here's
why water changes are essential, as well as a method of
calculating the necessary
amount. FAMA 12/79.
Ostrow, Marshall E. 1981. Water changes. TFH 5/81.i
Robert Fenner is the Author of the best selling book 'The Conscientious
and 'A Fishwatchers guide to the Saltwater Aquarium Fishes of the World'. He is a marine
scientist and an advid marine aqaurist. Robert Fenner is a former instructor for the
California system and has regularly contributed to reputable aquarium
Further information regarding Robert Fenner can be found at his website:
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