Fish, Tanks and Ponds

Fish, Tanks and Ponds
A comprehensive guide to fish

The importance of water testing

Flameback bleeding heart tetra, Hyphessobrycon pyrrhonotus
Flameback bleeding heart tetra


Regularly testing the water of your aquarium is one of the most important things that you can do. It will allow you to see potential problems before they become real actual problems, water tests can pin point the cause of illness in fishes and water tests will help you to determine how much and how often water changes need to occur. In short water testing has a vital role to play in the maintenance of any aquarium.

Which tests to use

Paper strip tests: Paper strips are one of the cheapest ways of testing the water with most tests carried out on one single strip. Unfortunately they have a very limited range and poor accuracy in comparison with other methods of testing. Paper strips are unlikely to pick up potential problems due to their lack of sensitivity and really these test strips are not recommended as the main method of testing the water.

Letting a shop do the testing: This is not very convenient and it can be expensive due to the number of tests required. When you notice that there might be a problem i.e. cloudy water, fish gasping and so on you really need to test the water immediately and this might not always be possible if a shop is doing the tests for you. One important point is that when you are given the results make sure that you get all the results in writing rather than a verbal "your water is ok" because knowing  the actual results can be important. Again this method is to flawed to have as the main testing system.

Liquid reagent test kits: Also known as dropper tests. These kits are very easy to use, reasonably priced and fairly sensitive and accurate. You can buy a kit which contains all the tests that most people need and then buy refills as they reagents are used up. All round these are the best option and most recommended.

Dry tab kits: As above but dry testing reagents have a much greater shelf life and are generally more accurate than liquid reagents, but the tests take longer to perform and the cost of each test is greater than liquid reagent tests.

Electronic meter tests: Are easily the most accurate and fastest method of testing but their price is out of range for most hobbyists. Electronic meters are more suited to commercial use where a lot of tanks need testing in a short time.

What to test for and why

Ammonia NH3 and Ammonium NH4: Ammonia is a deadly toxin to fish, in an established and well maintained aquarium it is very unlikely to be a problem since all the ammonia produced by the fish will be dealt with by the filters. Ammonia levels may rise if a lot of new fish are added in one go, if the fish are over fed, if a fish dies and lays undiscovered or if there is a filter failure. You may notice the fish become lethargic, begin flashing or they are panting heavily. These symptoms could have a number of causes and it is only by testing the water that the cause can be discovered and rectified.

Nitrite NO2: is in many ways similar to ammonia, it occurs as a natural part of of nitrification in all aquaria but its level should be so low that it is undetectable. If nitrite becomes detectable then there is a problem, the most likely causes of elevated nitrite levels are: Over feeding, immature filter system, poor filter maintenance or overstocking. Nitrite is a deadly toxin even at low levels and so the problem needs urgent treatment.

pH: Most fish have quite a narrow band of tolerance for pH and the pH has a tendency to fall as a result of nitrification. It is important that the pH is kept reasonably stable, again without the regular testing of the water the pH would be unknown and could fall to dangerous levels for the fish.

Nitrate NO3: Nitrate levels will rise in all aquaria because nitrate is in most cases the end product of the nitrification process. Nitrate is a very mild toxin to fish but it is a toxin non-the-less. High levels of nitrate can cause sterility and poor health in fish if the problem goes on for long enough. Monitoring the nitrate levels will act as a great guide for water changes. If insufficient water is changed the nitrate level will slowly rise so it is important that nitrate is kept an eye on to prevent this. If instead you used a standard 25% water change every two weeks and didn't check the nitrate level it is quite possible that the nitrates could reach dangerous levels within a few short months.

KH carbonate hardness: Carbonates will fall as a result of nitrification, if they fall to far the pH will suddenly crash and the fish will suffer as a result. Carbonates sacrifice themselves in order to maintain a stable pH and they also play an important role in nitrification which could stall if the KH drops to low. Water changes will help to replenish the carbonate level but in soft water areas this might not be enough so extra carbonate may need adding when changing the water. Without regular testing you would have no idea about any of this.

Most fish health problems are actually water chemistry or water quality problems and regular testing will act as a guide to maintaining the ideal parameters for your fish and will help to pinpoint a problem when it occurs.