Adjusting water hardness

4 Jan 2010
Sidcup, United Kingdom
My tank water parameters are as follows:-

PH 8.2
Ammonia 0 ppm
Nitrite 0 ppm
Nitrate 10-20 ppm
KH 12° dKH 215 ppm
GH 17° dGH 304 ppm

My tap water (water tested straight from tap) parameters are as follows:-

PH 7.2
Ammonia 0 ppm
Nitrite 0 ppm
Nitrate 10-20 ppm
KH 14° dKH 250 ppm
GH 19° dGH 340 ppm

I am planning to keep Rainbows, Amano Shrimps, Gouramis, Angel Fish, and Cardinal Tetras. I will also be planting many plants that mostly prefer softer water. I will be adding CO2 and dosing with dry fertilisers (EI Method).

I would like to reduce the hardness of my water if possible, I was planning to use half tap water and half RO Water.

I would ideally look to achieve a GH of around 10 dGH for the plants and fish. If I am using CO2 and dry fertilizers is there anything I should be aware of about doing this. Will the CO2 reduce the hardness?


27 Dec 2008

The co2 won't effect the hardness at all, it will change the ph however but this is nothing to worry about.

Mixing RO-tapwater will work fine and should bring the hardness down to the level that your aiming for and the only thing I can think of when dosing dry ferts is if your adding magnesium sulphate (mgso4). GH is primarily made up from disolved calcium and magnesium therefore excessive ammounts of magnesium in your fert mix if not used by the plants will over time raise the GH levels.

Many on here will question why you would want to aim for certain water parameters, some even ridiculing those that do. I'm not one of them, in fact I go even further and use 100% remineralised water 100% of the time. My gh is about 4-5 and kh 1-2. I don't really understand why if your willing to take it on you would only go halfway though (i.e. gh 10 kh 7 ish).

Regards, Chris.