As mentioned before, discus are very particular about the pH levels they need to survive. You need to keep the pH levels in the water between 5.5 and 7. If the pH levels go above 7, the discus become stressed and this can lead to severe health problems for them.
A healthy medium for the pH levels in the water in your discus tank is about 6, if you can maintain that level you won’t have any problems with your discus.
It is important to note that the alkalinity of the water is very closely tied to the pH levels. Water which has a higher hardness tends to be more alkaline, while water which tends to be on the soft side is generally more acidic.
This is due to what is known as the buffering capacity of the water. The buffering capacity of the water denotes the presence of alkalinity and this means that the water has the tendency to maintain a higher pH level. If your water is too hard, the pH level will stay high, too soft and your pH level will plummet. If you an maintain your water hardness between 10 degrees dH and 15 degrees dH, you should not have a problem controlling the pH level in your tank.
It is very important to check the pH level of the water frequently, especially when you change out some water, until you get the hang of how your water generally responds. There are two main choices for lowering the pH levels of the water in your discus tank if they get to be too high; phosphoric acid and peat moss:
Phosphoric Acid:
Using phosphoric acid is one of the easiest ways to quickly lower the pH level in the water, however it can have drastic effects on your overall water chemistry. You can purchase phosphoric acid in many forms, such as drops or powders, from your local aquarium supply store.
Peat Moss:
Using peat moss as a way to lower the pH level in your discuss tank, while not as fast acting as using phosphoric acid, Is the better of the two choices. The peat moss absorbs carbonates which cause the water hardness to be too high, while releasing acid into the water.
Once you become accustomed to its use, you should be able to control the pH levels of your tank, using only peat moss.