What should I do if I detect ammonia?

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Ammonia is the most toxic nitrogenous pollutant you're likely to encounter in your aquarium, so it's important to know exactly what to do if you detect it. Here's Matt Clarke's advice.

Check for nitrite

If ammonia is detected, test also for nitrite and check the pH and temperature of the water. Ammonia often goes hand in hand with nitrite problems, so you may have issues there too.

Check temperature and pH

Ammonia toxicity is also related to pH and temperature. It’s much more toxic to fish when they are in warmer water and when pH is higher. To find out how big your ammonia problem is, punch the values into our Ammonia Toxicity Calculator.

Increase aeration

Ammonia irritates the gills of the fish, causing them to produce extra mucus. Additional mucus reduces the surface area available for gaseous exchange and fish may gasp at the surface to try and get the oxygen they need — or lie on the bottom looking rough. Add any extra air stones you have, turn on your venturi or point your filter outlets towards the surface to raise oxygen levels.

Do a water change

Change 50-75% of your water and top up with dechlorinated tapwater of a similar temperature and chemistry to the water in your tank. This will quickly dilute the ammonia, making conditions safer, but the fix could only be temporary.

Find out why

If the ammonia has risen once it could rise again, so it’s vital to find out why it happened in the first place. Common reasons for raised ammonia levels include dead fish that have not been removed, feeding too much or too often, overstocking, washing filter media under the tap or replacing old with new, or adding fish to tanks with immature filtration.

Add an ammonia remover

To reduce further problems in the short term add either some ammonia-removing filter media, such as a zeolite-based product, or an ammonia neutralising liquid. Also try one of the more modern bacterial supplements that claim to boost filter bacteria populations.

Keep checking

Ammonia can return quickly and nitrite problems can follow soon after, so keep testing the water and making partial water changes until things return to normal.

This item was first published in the November 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.