FAQ: Water Care for fish

Dip the strip for the stated time, shake off the excess and compare the colours with the chart on the pack after the stated time. Do not handle strips with wet fingers and close the container tightly straight away, as moisture spoils them.

In a stable tank many fishkeepers test the main parameters every week or two, and nitrate before water changes. Test more often when fish behave unusually, after adding new fish, after treatment or after cleaning the filter.

Yes, liquid test reagents and strips age and can give false results, so check the expiry date on the pack. Store them in a cool, dry, dark place and replace them once expired.

Tests vary in accuracy, may be expired or badly stored, and colours are easy to read differently, especially under artificial light. If results disagree, repeat with a fresh test following the instructions, and look at the trend rather than a single number.

A kit with several core tests is often more convenient and cheaper per test, especially for a beginner. Individual tests are worth buying when you mostly check one or two parameters, such as nitrate or KH, and they run out faster than the rest.

Yes, electronic meters mostly measure pH, conductivity or total dissolved solids (TDS) and temperature. They are handy and accurate, but pH meters need regular calibration, and ammonia and nitrite are more often checked with chemical tests.

A TDS meter shows the total amount of dissolved substances in water. It is especially useful for shrimp tanks and when using reverse osmosis water, since it quickly shows whether the water is pure enough and correctly remineralised.

Keep tests tightly closed in a cool, dry, dark place out of reach of children and pets, since some reagents are chemicals. Do not leave them near the aquarium light or anywhere warm.

Some pet shops offer to test a water sample, and laboratories can do a more detailed analysis. Bring the sample in a clean, sealed container taken the same day, and ask which tests were used.

It is best taken before a water change and a few hours after feeding, from the middle of the water column away from the filter outlet. That way the results reflect the tank's usual state and can be compared with earlier ones.

Yes, records help you spot slow changes, such as rising nitrate or falling KH, before they become a problem. Note water changes, filter cleaning and new fish too, so you can see causes and effects.

A phosphate test is useful when the tank has a lot of algae, since excess phosphate feeds them. In a freshwater fish tank it does not need regular testing, but in heavily planted and marine aquariums phosphate is watched more closely.

A copper test is useful if your home has copper pipes, you use copper-based treatments or keep shrimp and snails, which are very sensitive to copper. Otherwise it rarely needs testing, and a conditioner that binds metals reduces the risk.

Oxygen tests exist, but in an ordinary tank fish behaviour is watched more often: if they gasp at the surface, oxygen may be short. A test is useful in heavily stocked, hot or densely planted tanks, especially in the morning.

Most popular freshwater fish do well at roughly pH 6.5–7.5, though South American fish often prefer more acidic water and African lake cichlids more alkaline water. A stable pH the fish are used to matters more than an exact figure.

Fish adapt to a fairly wide pH range, but sudden swings stress them and can damage their gills. So it is often safer to keep a steady, if not quite ideal, pH than to keep adjusting it with chemicals.

pH is usually raised by increasing carbonate hardness (KH): adding crushed coral to the filter, using limestone rocks or special buffer products. Change it gradually, test several times a day and follow the manufacturer's directions so the change is not sudden.

Peat in the filter, catappa leaves, alder cones, driftwood or mixing in reverse osmosis water, which lowers KH, all reduce pH gently. Chemical pH-down products act fast, but in hard water the pH often bounces back, so they are used with care.

pH gradually drops when the water is low in carbonate hardness (KH), which neutralises the acids produced by the nitrogen cycle and decaying organics. Infrequent water changes, heavy stocking or peat speed this up, so regular water changes and watching KH help.

It is a sudden drop in pH when the water's buffering capacity (KH) runs out and acids are no longer neutralised. It can stress or kill fish and stall the filter bacteria, so in soft-water tanks regular KH testing and water changes are important.