Duradrakon hardening salt
Hardening salt mixture for reverse osmosis water
Pure RO water is not suitable for direct use in the aquarium, except in a few special cases (pure flow-through tank, black water biotope). The few minerals it still contains would be used up too quickly. It is therefore sensible and correct to harden the water used to a carbonate hardness of 1 - 3 °dH to supply fish and plants. If you do not want to or cannot do this by blending with tap water (e.g. source water that is too heavily contaminated!), you will need a hardening salt that supplies the water with a defined quantity of minerals.
- The ion standard ratio is set approximately
- The supply of all trace elements is guaranteed
- No chemical tricks such as the addition of organic or acidic salts are used (therefore no oxygen consumption or strange pH jumps during use)
Requirements
This hardening salt is only suitable for aquarium water with sufficient free CO₂ (preferably from a regulated CO₂ system) and a pH of well below 7, as otherwise some components will only dissolve very slowly or not completely!
For Malawi and Tanganyika lake tanks other hardening salt mixtures should be used.
Composition
22.2 % carbonate, 17.0 % hydrogen carbonate, 16.8 % calcium, 12.9 % sulphate, 8.1 % chloride, 5.7 % sodium, 4.6 % magnesium, 2.1 % potassium, 0.05 % trace elements, remainder: crystal water
At a dosage of 10 g per 100 litres of fresh water, this corresponds approximately to the following addition of important substances:
62 mg/l hydrogen carbonate, 17 mg/l calcium, 13 mg/l sulphate, 8 mg/l chloride, 6 mg/l sodium, 5 mg/l magnesium, 2 mg/l potassium
Dosage
3.5 g salt mixture / 100 litres of osmosis water results in 1.0 °dH KH or 1.2 °dH GH
2.9 g salt mixture / 100 litres of osmosis water results in 0.8 °dH KH or 1.0 °dH GH
Standard kitchen units of measurement
- Levelled teaspoon: 1.6 g
- Heaped teaspoon: 6.4 g
- 5 ml measuring spoon (as often enclosed in medicine packs): 2,9 g
Use
The poorly soluble calcium carbonate contained in the mixture dissolves under CO₂ consumption in the form of soluble calcium hydrogen carbonate (which breaks down again into CO₂ and calcium carbonate during drying, which is why it only exists in solution). The more free CO₂ is present, or the lower the pH, the faster this process can take place.
At pH 6.0, this can happen in minutes, especially with a readjusting CO₂ system, but at pH just below neutral and relatively little CO₂ in the water, it can also take a few hours.
The slight turbidity that forms for a short time is harmless for fish and plants.
You can Duradrakon by circulating it vigorously in an external water treatment system before changing the water.
If neither method is practicable, the very easily soluble mixtures Duradrakon GH-Plus and Duradrakon KH-Plus is also possible.
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1 - 10 of 26 reviews
15 May 2025 18:51
Duradrakon is my favourite
I really like using this salt, even if it takes a little longer to dissolve. Very balanced nutrient ratios. Works without any problems, I've been using it for a long time.
I have now also added Duradrakon GH+ and Duradrakon KH+. This allows me to adjust the water values in my aquariums as required and very well.
28 January 2025 00:00
Low salt content...
Low salt content for the required hardness.
20 August 2024 00:00
1a product
1a product. I have been using it for years.
27 June 2024 00:00
Valuation without text
Valuation without text
13 January 2024 13:08
Very good article
I also use the product from time to time. It works perfectly for me. I solve the problem of solubility with mineral water, in which I dissolve it a little beforehand. It is then added to the changing water and circulated for a few hours.
15 October 2022 20:16
Only Duradrakon
Super balanced nutrient ratio. There is no better hardening salt for me and my aquarium!
21 January 2021 16:25
Great hardening salt with potential for improvement
I have been using Duradrakon for a long time. In my opinion, it is the best product on the market.
Only the solubility leaves something to be desired.
It would be great to be able to buy the dissolved product in liquid form.
7 July 2020 09:18
Very good quality
You can use it to harden the water to exactly the desired hardness
15 January 2020 12:34
Good product, just quality from DRAK
For about two months I have been using only osmosis water for the weekly water change (60%). It is hardened with Duradrakon, 8g per 75 litres. The salt is completely dissolved after about an hour and the aquarium water is clear again. Salt is certainly available at a lower price, but with Duradrakon you get the usual high quality from DRAK. I also use Eudrakon N, Eudrakon P and Kramer Drak in my tanks and they run really well.
With DRAK, you always have a precise list of ingredients on the products.
The delivery time is unbeatable.
5 January 2018 13:51
KH is not achieved with CO₂ control
When used without a CO₂ system, the dosage is exactly correct and the desired values are achieved perfectly.
When using a regulated CO₂ system (pH set to 6.65), the KH cannot be adjusted even after repeated dosing. The GH increases all the more. After just 1-2 days, the KH has dropped again to such an extent that the CO₂ control switches off completely.
Could it be that the CO₂ greatly reduces or neutralises the KH?
With an alternative product (from D******e), dosing the KH worked without any problems, but the GH rose disproportionately high over time, which is why I wanted to try Drak.
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