Water chemistry is essential for the survival of fish and aquatic plants. Some factors need close attention like pH, KH, GH and other parameters. So, there should be regular testing to balance all these elements. To do so, you must know what type of fish you have and in which condition they are more likely to survive.
pH is a measurement of the acidity or alkalinity of the aquarium water. Seven is neutral, above 7 and up to 14 is alkaline and below 7 to 0 is acidic. All fish species have preferences in which to live but will adjust to survive. Changing the pH can be difficult and must be done with caution. For example, using liquid pH can cause a dramatic change in the water since it is only a short-term solution. To change the pH, you must change the water buffer level.
Ammonia and Nitrites [NH3]
Fish waste and excretion produce ammonia. Ammonia is toxic to fish and can be removed by filtration. If you have a high level of nitrite or ammonia in the water, it could be the filtration needs to clean or remove. It can also be due to overfeeding. To resolve or decrease nitrite or ammonia, clean your filter system weekly or remove larger water quantity. You can also use water dechlorinate solution to neutralize the water.
Nitrates are not as toxic as ammonia or nitrite but with high levels, fish could lose their color or appetite. Having plants in your aquarium can assist with reducing nitrate since plants uptake includes nitrogen, potassium, and phosphorous. An aquarium with both plants and fish will require fewer fertilizers since the fish is providing fertilizer to the plant.
KH and GH
KH refers to how much carbonate is in the water. To raise the KH, simply use a small amount of sodium bicarbonate. It is best to do this when you are changing the water. Another way to raise the KH is to add crushed coral in the filter. Add small amount because coral will raise the pH. GH is the hardness of the water. Generally, the higher the pH, the higher the GH. If you add limestone chips in a filter bag, it will increase the GH. Adding coral to the tank or the filter bag will do the same. To lower the GH, add small bags of peat, wood or plant substrate will do the trick.
To do any changes to your water chemistry seek professional help. You might just end up doing more than you need and that could end in a disaster. If your fish are surviving just fine, they have already adjusted to the water and there may be no need to do anything with the water chemistry.