The natural inhabitants of your tank produce acids that lower the pH of your tank if you don't have any buffering capacity (low alkalinity, very low KH
). Fish waste is acidic, driftwood leaches acids, plant waste is acidic, dead and decaying organic matter (plants, fish, food) is all acidic. It is important to maintain a certain level of buffering capacity in order to buffer against these natural acids.
In your case, I highly recommend getting KH
test kits. You may have very little buffering capacity/low alkalinity/very low KH
. You want a KH
of at least 4, but 7 will give you good stability. GH
also plays a role in your pH, indirectly. In order to have a stable pH, your GH
needs to be higher than your KH
. Test your GH
, your KH
, and see what the issue is.
In order to increase your KH
, add 1/4 tsp of BAKING SODA (sodium bicarbonate) to your tank (directly in the HOB
is fine) per every 5 gallons of water to increase your KH
by about 1.5 degrees. As your KH
rises, your pH will follow. Only dose your tank once per day at 1/4 tsp per 5 gallons. This will only result in small pH shifts and will not harm the fish. After you reach your desired KH
, you can stop adding the baking soda, but continue testing teh KH
for the next week to ensure everything has balanced out. Once everything is balanced, you do not need to add any more baking soda to your tank, just be sure to buffer your tap water (add baking soda) so it matches the KH
& pH of the water you are replacing.
If you have very low GH
, where your GH
is currently lower than your KH
or will be lower than your GH
once your increase your KH
you need to re-mineralize your water. There are many products that do this well. Seachem's equilibrium, as well as any "cichlid salts" that are sold. follow the directions on the bottle to increase your GH
to your desired level.
If you don't want to buy anything, you can use Epsom Salt (Magnesium Sulfate) add 1/2 tsp of epsom salt per 5 gallons of water to increase your GH
by about 1.5 degrees. You need to dissolve the epsom salt in water before you add it to your tank.
You might want to aim for a KH
of 6 and a GH
If you don't have a planted tank and don't have high-intensity lights or prolonged lighting times you want to first try add Seachem Neutral Regulator. It will buffer your tank to 7.0 and help maintain it there, but it is phosphate based, so it can lead to increased algae growth in the right circumstances.