Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
pH is not a stand alone value. It is based on what minerals, acids and salts are in the water.
Control the other things, and the pH will take care of itself.
Ask about any of these terms until you understand them, then decide whether you really need to monkey around with the pH.
GH is the General Hardness. It is a measure of the calcium and magnesium in the tank. This is the factor that you want to get right for the fish you keep. Your fish are soft water fish, but have been bred in captivity for so long that they will accept a wide range of mineral levels.
KH is Carbonate Hardness. This is one of the most common buffers of pH in the aquarium. High KH generally means high pH. Low KH generally means the pH is free to change, so something else will dictate what the pH might be.
pH is actually a way of telling you if there is an excess of H+ or OH- in the water. Fish can handle a very wide range of pH, and changes in pH as long as their mineral level requirements are met.
Rift Lake Cichlids come from water that has a very high mineral level. GH and KH way up over 10 German degrees of hardness. The high KH makes the pH in the upper 7s to mid 8s.
Soft water fish (most rain forest river fish) come from water that has a very low GH and KH. Lots of leaves fall in the water, too, so there are a lot of organic acids in some of these waters. The low KH allows 'something else' to dictate the pH. The organic acids make the water acidic.
Here is a test you could do:
Run some tap water into a bucket. Maybe a gallon or two.
Add 1-2 handfuls of peat moss.
Stir often, such as several times per day.
Test GH, KH and pH daily for 2-3 days.
If this does what you want, then add some peat moss to the filter. I use a nylon stocking, cut into sections, as a media bag.
When you are getting ready to do a water change, run the water into a bucket the day before, and add peat moss. Usually the peat moss does the job over night, and you would do the water change the next day. I use a nylon stocking and a small fountain pump to circulate the water when I prepare the water this way.