It is always easier to increase a waters’ hardness or alkalinity, but not so easy to lower it. In order to change the hardness or alkalinity in the water, you first need to understand what it is exactly that you are dealing with.
Water hardness is simply the sum of the amount of the carbonate and non carbonate hardness of the water you are testing. The total hardness of a water is measured in degrees dH. You do not need to concern yourself too much with total hardness when it comes to breeding or keeping discus fish. The number you are going to be more concerned with is the temporary hardness or the levels of calcium and magnesium in the water.
The water hardness you will require for properly keeping discus fish is in the 12 degrees dH to 17 degrees dH range for optimum results. The calcium levels you will maintain in conjunction with those values is in the 200 milligrams to 300 milligrams per Liter range.
Controlling Water Hardness:
As long as you maintain the water hardness as close as possible in the ranges of the values mentioned above, you will not be required to take much action in terms of trying to reduce or increase the water hardness in your Discus fish tank.
If you do need to lower the hardness of the water in your discus fish tank, you can always throw in some driftwood or peat to accomplish this task. It is important to note that the water hardness will not adjust instantly. So before you go adding in additional driftwood or peat to additionally lower the water hardness in your discus fish tank, be sure to let the water be for a good six to eight hours to see how the first batch you threw in effects the water hardness.
If you need faster results, or don’t wish to go fiddling with driftwood and peat, you may consider investing in a reverse osmosis, or de-ionization machine. While these will help get the job done faster and will give better results, you will be removing essential trace elements from the water that will need to be replaced before you can use it in your discus fish tank.
You can purchase reconstituted salts from many aquarium supply stores, in order to replace any essential trace elements you may have removed with the use of the above machines.
Some experts recommend that as an alternative to buying these reconstituted salts, that you can simply throw in about 5% mix of your own tap water. However, this may not be viable solution for you, depending on the levels of chloramines you may have in your tap water.
Some people seem to think that simply running the water through your household water softener will do the trick if the water hardness is too high. This is not the case. Household water softeners are completely unsuitable for this task as they add sodium ions to the water.
Sodium ions are, depending on the levels, detrimental to discus so as you can see that isn’t a good option for preparing the water for your discus.