1. What is KH and GH?
Although KH might sound complicated it really isn't. In it's simplest, KH or carbonate hardness is what stabilizes your ph. The lower your KH is the more you pH will change and fluctuate. Most water naturally has a stable and high enough KH meaning you don't need to worry about it. However if you find your pH is changing regularly it may be time for a KH test. An added benefit of KH is at high levels it will also benefit aquarium plants along with GH.
GH or total hardness is different as it essentially measures how much calcium is in your water. Calcium can be either a positive or a negative thing to have and it really depends on the fish. So make sure to research what GH or total hardness fish require. Some fish will live in a vast variety while some won't and some will only spawn at a certain GH.
2. How increase KH and GH?
KH and GH can be increased simultaneously using different natural stones. The most common being limestone and crushed coral which can be bought in filtration bags and added into the aquarium filter. As for how much you should add, it is debatable but it should be added and tested to see the affect it has had. This media should be changed every 6-12 months.
If you only want to increase KH but not GH look into dosing Sodium Carbonate or baking soda in your aquarium. Although it sounds odd it can work as long as you find the recommended dosage.
To increase GH without changing KH you need to add aquarium branded calcium and magnesium. Make sure it isn't branded as a carbonate or a bicarbonate as it will raise both KH and GH.
3. How to lower KH and GH?
Lowering KH on its own can be done quite easily using natural items. These items include cattappa leaves and aquarium peat. Adding them releases tannins into you water and can also affect your pH so keep that in mind. Other options include using altered water from a RODI or reverse osmosis unit, in simple terms a water purifier.
To lower GH by itself is most easily done via a RODI unit would to supply your aquarium water or frequent water changes. Other methods include specialized crystals filter pads and the lowering of ph. Easier methods should be prioritized if lowering GH.
4. Testing KH & GH
As the two do go hand in hand you can find many test kits that combine the two as a set. As long as you follow the directed instructions you shouldn't go wrong! Not only this but most brands should show the appropriate levels of each depending on what type of fish you have. If not make sure to research what KH and GH you fish like before purchasing or altering your water.
