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Frequent Partial Water Changes
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 on a regular basis. This article deals with the reasons for, and some rules of thumb as to how often, how much and how to make these changes.
Rationale:
There are several major benefits of frequent partial water changes. Dilution of nutrient, removal of particulate matter, removal of toxic, stagnant material, reduction of thermo and chemoclines. Results anticipater are faster, more vigorous growth, reduced algae growth and odor.
It has been written in many fisheries, limnological and hobbyist texts that along with temperature and photosynthesis, metabolite wastes build-up is one of the three most important factors influencing the health, growth and reproduction of fishes. 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 chemical « stuff » fishes and ponds cycle is toxic. Some metabolites, like pheromones, are actually known to have calming effects. Therefore the concept of partial, not total water changes.
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 accomplished. Most common are some forms of chemical filtration like carbon and ion-exchange materials. These are useful but often labor and money intensive. Moreover, these chemical filtrants do remove desirable chemicals as well.
It is vital that as much extraneous materials : leaves, dirt, landscape and rain run-off, etc., be kept from getting in the system. What little does make its way in should be removed by netting, diluted or removed by making partial water changes.
Some potential pollution will probably be added to your system in the way of food and fertilizer. Even without over- or mis-feeding and/or fertilizing, water evaporation has a decided negative chemical effect on an aquatic system. This 'Salton Sea Syndrome' occurs as water evaporates leaving behind its chemical constituents.
Before building a water effect, planning must be directed at the source of water and nutrient and allowances made for occasional or continual dilution and freshening of the water. So enough of the reasoning for making water changes ; onto the nuts and bolts:
How Often :
Depending on your pump/filter/circulation system, stocking and feeding regimen et. Al., partial water changes about once a week during the warmer months are about right. More frequent smaller amounts are better than infrequent mega-changes.
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.
How Much :
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 avoided. By and large, water treatment chemicals are unwarranted (except for de-clorinator) with such frequent small percentage changes.
How To :
However it is achieved, the part of the water and what's dissolved and suspended in it you want to get rid of is on the bottom. Overfilling, draining your syustem at the surface will not get you the results that you are looking for.
In the happiest of circumstances you have a sump area with a slope over the surface of the basin leading to it. You open a valve or drop in a submersible pump and voilą ! the 'bad' water and solids are whisked away.
In the second best scenario you have a skimmer system you can hook a vac-line to and suck out the bottom material. Less desirable routines involve a 'skid-unit' with a gas or electric powered pump or a change in elevation to siphon off wastes from the bottom.
Whatever way it is done, change some of your water on a regular basis. 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 continuing success.
Excerpted from « Practical Koi Keeping », Vol. 3 Authored by Bob Fenner
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