Water Testing – Nitrite/Nitrate


Nitrite is the by-product of the breakdown of Ammonia, this breakdown is done by the bacteria, nitrosomonas, in your pond. High levels of Nitrite in your pond can cause damage to the fish liver, spleen, nervous system and kidneys. This can result in the death of your fish. Nitrite is converted to Nitrate by nitrobacteria in your pond. The nitrate is removed from your pond by the plants or algae that may be present. Nitrate has a very low toxicity to your fish and is generally never a problem. Plants use Nitrate as a main growing nutrient. Both nitrosomonas and nitrobacteria are both good bacteria that naturally occur in your pond environment, they may also be known as filter bacteria. When the level of good bacteria in your pond is not sufficient to deal with the amount of waste being produced, Ammonia and Nitrite can rise to toxic levels.   

High levels of Nitrite can cause ‘Brown Blood Disease’ – This condition, as the name states, turns the blood brown from the increase of methemoglobin. Methemoglobin cannot bind to oxygen so the blood cannot carry oxygen resulting in the fish suffocating. Increasing the oxygen levels in the pond will not change the situation. Signs that your fish may be suffering from this or from nitrite poisoning are as follows:

  • Tan or Brown Gills
  • Gasping at surface
  • Hanging near water outlets
  • Rapid Gill movement
  • Laying on the bottom of the pond

Generally when it comes to any kind of sickness the fish will not eat. This is not always the case with nitrite poisoning. They may look lethargic and lay on the bottom of the pond, but will still come up for food and then return to their lethargic state again. 

Generally when fish are looking ill the first thing you do is a water test to establish the cause. You can test the Nitrite levels with the PondCare Master Test Kit, which also has Ammonia, Phosphate and pH tests included or you can buy the Nitrite Test Kit separately, or you can bring a water sample into the store and we will test it for you for a small fee. To treat high levels of Nitrite you should:

  • Do a partial water change (25%). Re-filling the pond will not remove the Nitrite but will dilute it. Make sure to use a Chlorine neutraliser when you are filling the pond back up. Using Stress Coat is ideal as it contains added benefits for protecting the fish. Topping up your pond without using a chlorine neutraliser can kill off the good bacteria which then leads to ammonia and nitrite build up.
  • Add Beneficial Bacteria. You can use either PondMax Clarifier Bacteria or Lysofoss.  Lysofoss works quicker than normal filter bacteria and will also help to control bad bacteria, reduce disease and stress and can control phosphorus, ammonia and nitrogen levels. To get the bacteria to thrive quicker you can also add The Water Cleanser Block to your pond. This wax block is designed to help keep your water crystal clear but it will also provide the bacteria with an area to colonize and thrive in.  
  • You can add Salt to the water, as this will reduce the toxicity of nitrite. Salt will increase the chloride ions in the water, which block the nitrite molecules. It won’t completely fix the situation as they will not block all the nitrite molecules but it will defiantly give the fish that little bit of relief. The Dosage rate of salt is 1kg to 1000 litres of pond water. Salt should not be re-applied as it doesn’t evaporate or filter out of the water. The only way to get rid of it is to do a water change and even then you may still have salt present.

You can drop in to The Pond Shop with a water sample and we can perform a Water Test for just $3.00. If you have any concerns or would like to speak to someone about a particular problem you are having with your pond you can send us an e-mail, give us a call or come and speak with us in the shop. 

E-mail – sales@thepondshop.com.au
Phone – (08) 9250 6063