Water Quality

Setting water values

Fine-tuning water values to your fishes' needs

Water hardness and pH value ("acidity") are the most important parameters for fish. Tap water which is too hard can be softened with Dennerle reverse osmosis systems. The pH value can be set to the required level by adding CO2. When the water is too soft, the water hardness (total hardness and carbonate hardness) can be increased in a controlled manner with Dennerle GH/KH+ and KH+.

A crucial factor in aquarium water

The carbonate hardness forms the crucial buffer system in an aquarium. It prevents excessive variations in the pH value, which would have adverse effects on fish and plants. Many popular aquarium fish require a higher level of carbonate hardness than tap water is able to offer. The carbonate hardness in aquarium water may also be reduced as a result of various processes (biogenic decalcification, nitrification).
The carbonate hardness should thus be checked on a regular basis and kept to a level in keeping with the needs of the fish in the aquarium.

Professional tips:

The carbonate hardness should ideally amount to 50 - 80 % of the total hardness, e.g. GH 10 °d, KH 5 - 8 °d.
DENNERLE GH/KH+ provides a swift and simple means of adapting total hardness to the given requirements.
We recommend DENNERLE Elements+ for replenishing the trace element content in osmosis water and for fish aquaria.
For aquaria with plants we recommend supplying the necessary trace elements by using S7 VitaMix as part of the DENNERLE fertilization system.

Testing water quality

Aquaria which are set up according to the DENNERLE system virtually rule out problems from the outset. For safety's sake, regular monitoring of the key aquarium water values is nevertheless extremely important.
DENNERLE Immersion Tests enable straightforward measuring in a matter of minutes.

The ideal values for aquarium water (community fresh water aquaria):

Carbonate hardness 1-4 °d.
Total hardness 4-7 °d
pH value 6.4 – 6.9
CO2 content 20 – 35 mg/l
O2 content, in the morning 3-5 mg/l
O2 content, in the evening 5-8 mg/lKarbonathärte 1-4 °d

What needs measuring, and when?

When the following changes take place in the aquarium:

  • Water changing: When new water is added to the aquarium, e.g. osmosis water: KH, total hardness, pH, CO2, O2, nitrate.
  • When replacing old lamps: pH, CO2, O2  over approx. 4 weeks; measure daily at first, then later every 2-4 days, adjusting the supply of CO2 accordingly.
  • When introducing new fish: pH value, O2, nitrite and nitrate in particular prior to introducing new fish and in the first few days after introduction.
  • When setting up a new aquarium or carrying out extensive rearrangement: pH, CO2, O2  ammonium/ammonia over approx. 4 weeks; measure daily at first, then later every 2-4 days, adjusting the supply of CO2 accordingly.
  • If fish behave unusually, e.g. gasping for air or "darting about": pH, O2, ammonium/ammonia, nitrite, nitrate