Suitable water values in the pond: OASE online laboratory

Do you know what the pH of your pond water should be? What about the nitrate level? In this article we’ll help you understand the ideal values for all the main parameters to keep your pond healthy.

pH

Optimal value

The optimal pH value for your pond should be between 7.5 and 8.5. If you want to change the pH value, you should always proceed very carefully to avoid large pH jumps.

Measures

Counter a pH value that differs significantly from the recommendations by changing the pond water. Excessive pH values can be lowered with OASE AquaHumin; pH values that are too low should be increased with OASE OptiPond.

Carbonate Hardness (KH)

Optimal value

The optimal level of carbonate hardness for garden ponds is a minimum of 5 °dKH.

Measures

If the carbonate hardness is under 5°dKH you should use OASE OptiPond.

Total Hardness (GH)

Optimal value

Most pond fish feel comfortable in medium-hard water (10–15 °dH).

Measures

We do not recommend lowering the hardness. You can increase the hardness by using AquaActiv OptiPond pond water stabiliser.

Nitrite/Nitrate (NO2 / NO3)

Optimal value

Nitrite: Optimally the nitrite concentration should be in the non-measurable range. From a nitrite content of as low as 0.05 mg/l disturbances can occur for sensitive fish. At values higher than 0.5 mg/l permanent harm can occur.

Nitrate: In general, for the garden pond, a nitrate value of less than 20 mg/l is sought. However values to 50 mg/l are also bearable; the type and density of the fish stock must be taken into account. However values greater than 100 mg/l should always be avoided.

Measures

If there is excessive nitrite and/or nitrate concentration in the water we recommend:  

  1. Checking and possibly reducing the amount of fish food
  2. Changing part of the water if nitrite values are greater than 0.5 mg/l
  3. Checking and possibly regulating the fish stock
  4. Use of an OASE filter system if possible with supplemental aeration
  5. Use of OASE BioKick Premium

Most importantly, at the beginning of the pond season, and for new filter systems, the nitrite value should be checked regularly because a so-called "nitrite peak” (increased nitrite values) is usual for biology that is establishing itself.

Ammoniak-/Ammonium (NH3/NH4)

Optimal value

In the garden pond under the usual conditions a total ammonium concentration of 0.1 mg/l is considered normal; however an upper limit of 0.5 mg/l should not be exceeded. The determining factor however is the pure ammonia concentration that occurs from the total ammonia / ammonium concentration depending on the temperature and the pH value. The crucial values are listed in the table below.  

From approximately 0.05 mg/l ammonia: Damage possible.

From approximately 0.1 mg/l ammonia: Life-threatening damage is probable.  

Thus at 25 °C a total concentration NH3 /NH4 + of 4 mg/l at a pH value of 7.0 corresponds to an ammonia concentration of 0.02 mg/l, which is considered safe. However if under the same conditions the pH value is 8.0, this means an NH3 concentration of 0.2 m/l, and with a high degree of probability will result in life-threatening consequences.  

Measures

If there is an excessive total ammonia / ammonium concentration in the water we recommend:  

  1. Checking and possibly reducing the amount of fish food
  2. If the values are critical and there is fish stock, replace part of the pond water immediately
  3. Cleaning the pool and removing any dead organisms
  4. Use of an OASE filter system
  5. Adding OASE BioKick Premium, OASE AquaHumin or OASE OptiPond can be used to reduce the pH value and effect the associated detoxification of ammonia.

Phosphate (PO4)

Optimal value

For the garden pond a value to 0.5 mg of phosphate per litre is acceptable; the value of 1 mg/l should not be exceeded. A concentration of 0.02 mg/l is considered sufficient for the nutrient supply of water plants and inhibits algae growth. 

Measures

If there is excessive phosphate concentration in the water we recommend: 

  1. Checking and possibly reducing the amount of fish food
  2. Use of PhosLess Direct
  3. Checking and possibly regulating the fish stock
  4. Extending the plantings and removing phosphatecontaining silt, e.g. with the OASE Pondovac pond vacuum
  5. Use of OASE AquaActiv PhosLess Algae Protection. The filter media tubes bind phosphates from up to 5 kg of fish food.

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