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Monitoring your water quality by performing regular routine tests is important in maintaining clear water and healthy fish.  In general, test weekly at first, then every two weeks once you are getting consistent and acceptable test results.  Keep a log of your test results for reference so that you can easily detect gradual changes before any serious problems begin.

Once the water is testing perfectly for several weeks, the water is clear and the fish are active and healthy, many casual pond keepers tend to become complacent and begin to neglect testing as often as necessary.  The danger here is that sudden changes in temperature, anaerobic bacteria growth, rainfall and other factors can quickly change pristine healthy conditions to deadly ones.  Only regular testing will give you the information you need to be in control of the water quality in your pond.  Remember that water clarity and water quality are not one in the same.

pH Test twice weekly

pH is the measure of both acidity and alkalinity on a logarithmic scale
with values running from 0 (acid) to 14 (alkaline), with 7.0 being neutral.
Logarithmic means that a pH of 6.0 is ten times more acidic than 7.0 and
100 times more acidic than 8.0.  The ideal pH for most pond life, plants and fish, is 7.5, with an acceptable range from 6.5 to 8.5.

• The pH of your water changes throughout the day, slowly growing in alkalinity.  For the most accurate reading, test within a few hours of sun-up.  Always test at about the same time of day.
• The pH should be as close to 7.5 as possible, but most plants and fish will tolerate a pH range of 6.5 to 8.5.
• Test for pH on a bi-weekly basis for maintenance, or any time there is an algae bloom or other problem.  Use a wide range test kit such as Pond Care pH test which has a range from 5.0 to 9.0.

Alkalinity Test twice a year

The molecule responsible for stabilizing pH is called the carbonate molecule.  A measure of carbonate molecules is expressed as the total alkalinity (TA) or the carbonate hardness (KH).  Carbonate molecules are an exhaustible resource.  The effect of the carbonates becoming exhausted is a sudden drop in pH, which can, and most often does, kill fish.

• A high TA, 100ppm or above, will keep your pH stable for a long time.
• A low TA, 50ppm or less, will need to be remedied or there is risk of a sudden drop or ‘pH crash’, which can be deadly.
• Water in the eastern US tends to have a low TA, below 50ppm.
• To RAISE alkalinity without adding hardness add sodium bicarbonate, NaHCO3, (baking soda).
• Never use swimming pool chemicals to adjust the pH in your pond.

Oxygen Test as necessary

Be sure your pond is well aerated at all times.  If your fish seem lethargic, or are at the top ‘mouthing’ the surface of the water, your oxygen level is likely getting dangerously low.  If you see this happening increase circulation and aeration, and test oxygen levels immediately.

• When oxygen levels get low the largest fish suffer first.
• Dissolved oxygen level should be kept at or above 7ppm.  You can not have too much oxygen in your pond.
• Warm water holds much less oxygen than cold water so increased circulation becomes more important as the water becomes warmer.
• Plants use oxygen at night, lowering your dissolved oxygen level, so never turn off your circulation pump in the evening.
• Always keep a hole in the ice during the winter months to allow toxic gases to escape. (see separate article on how to over-winter fish)

Ammonia Test bi-weekly

• Ammonia in the pond is produced by organic wastes (fish waste, decaying plants, or overfeeding).
• Ammonia is very toxic to fish and becomes more toxic as the pH rises.
• Ammonia level should read 0 ppm.
• Test bi-weekly or any time there is a noticeable change in fish behavior.
• If ammonia level is high an IMMEDIATE water change of 25-50% should be done.  Be sure to use a de-chlorinator if using water from a chlorinated system.

Nitrites Test bi-weekly

• Nitrites are created through the breakdown of ammonia by bacteria.
• Nitrites are toxic to fish.
• Test level should read 0 ppm.
• Test bi-weekly or any time there is a noticeable change in fish behavior.

Bacteria

• Bacteria are essential to all healthy ponds.  Beneficial bacteria consume algae and break down ammonia and nitrites.
• Bacteria levels cannot be tested by the average pond keeper.  Follow directions on bottle to determine the dosage and frequency.

A positive ammonia test or nitrite test is one indication that bacteria counts are too low.

Stress Coat

• Enhances fish slime coat to resist parasites and other pathogens, improve gill function and speed the healing process.
• Stress coat should be added every two to four weeks or any time fish are handled and whenever new fish are introduced.

Salt

Pond Salt eliminates many fish parasites quickly.

• Ponds Salt adds electrolytes to the water which aid in keeping the gills functioning efficiently and help to prevent a variety of fish health problems.
• Ponds with plants and fish should have a salt level of .1% solution.
• Ponds with fish only should have a salt concentration of .2 to .3%.
• Test monthly or any time you have a water loss (not due to evaporation).  The most important times for salt are the transitional weeks as your fish begin to slow down in the fall and then come back to life again in the spring.
• Salt is used both as a preventative measure and, at higher concentrations, a cure for many fish health problems.