Some fish keepers never seem to have problems. Their aquariums are crystal clear, the fish are healthy and their plants are flourishing. These aquarists have experience. They know how often (and how well) to clean their filters, they know exactly how much water to change and how often - they have learned to manage their aquarium system. Guaranteed they did not learn this overnight or without making mistakes themselves. Undoubtedly, the majority of advanced fish keepers will have used a test kit to help assess tank conditions and diagnose problems at some point.

There is also a great piece of advice in fish keeping circles - "if it ain't broke, don't fix it!" While this statement certainly holds true, there is no harm in checking that things are OK. If things do go wrong then you may not be able to fix them in time. Perhaps "prevention is better that the cure" is a more apt piece of advice. This prevention can come in the form of periodically testing various water parameters to monitor water quality. I say "periodically testing" because depending on the maturity of the tank and its contents, the frequency of tests will vary. I recommend that water in a newly set up aquarium should be checked, to assess cycling progress, every 2-3 days and a mature aquarium should be monitored every 2-4 weeks, depending on the sensitivity of species, to ensure things are running smoothly. Additionally, just as you may have learned to get a feel for tank temperature by touch, you will learn when nitrates in your tank begin to rise or pH is about to crash without testing the water.

Generally, five water parameters concern the hobbyist. The levels of ammonia, nitrite, and nitrate present, the water hardness and pH. (Refer to the Water Chemistry Section to find out why these are important). As test kits are invariably expensive items possibly due to the chemicals contained within them or to the accuracy to which modern kits measure. It may therefore be prudent to think why you need to test the water and what to test.

Take a look at the following:

Suppose you have a mature aquarium and you wish to assess your tank's hygiene. Nitrate will naturally be present but there may also be an increase in ammonia, the first product of the nitrogen cycle indicating the filter cannot cope with processing the waste. On the other hand a rise in carbon dioxide caused by an increase in decaying materials will cause a pH drop. This too indicates poor tank maintenance.

To confuse the issue further, a pH drop maybe the result of a decrease in hardness caused by calcium and magnesium carbonates in the decor reacting with carbonic acid, which is also a by-product of decaying matter. So should one test for ammonia, pH or hardness?

A good understanding of water chemistry will help you decide.

Unless attempting to solve a particular problem, and an initial period of water testing to assess water type and stability, and to get a "feel" for your water parameters, checks are generally only necessary periodically to ensure that the right environmental conditions are being maintained for the fish you keep. Remember that fluctuations in any area stress fish so in some instances so may be worth checking more often.

As for the test kit itself there are three main options:

• Dip Tests - These are strips of paper that change colour to indicate the value of a given parameter. The colour can be compared against a guide on the box to assess the reading. The tests are quick to react and many dip tests allow several parameters to be assessed on one strip. On the downside they are very expensive and it can be difficult to match the colour change on the wet strip with the guide on the box.
• Liquid Tests - These are my preferred choice. Collect a water sample in the clear vile supplied, add a few drops of liquid, shake well and wait. After approximately 10 minutes the water will have changed colour and can be compared to the scale on the box. Because light can pass through the water it is very easy to obtain an accurate reading.
• Tablet Tests - Very similar to the liquid tests except that a tablet opposed to a liquid is added to the water sample. The tablet must then be crushed using the glass rod supplied until it dissolves - this can be frustrating. Again the results are easy to compare against the chart.

Two final pieces of advice firstly, when comparing test kits for value note the number of tests each provide. Secondly, the results of your tests will only be of value if you write them down and compare them with subsequent readings.