Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
pH is not a stand alone value.
It is controlled by what else is in the water.
The answer is this: If you want to control the pH, you have to control the minerals and salts that affect it.
Fish want a particular mineral level, not a particular pH. This can be tested with the GH test, and the TDS meter. Low mineral levels are low GH and low TDS. Make the GH right, get the KH similar, and let the pH do what it want. The TDS will probably also be in the right range when the GH and KH are right, because of the way I suggest you correct things.
Test GH, KH, TDS of the tap water, test the pH right out of the tap, and then allow a glass of water to sit out and test the pH at 24 hours and at 48 hours. Post these results here. Include the units.
High pH can be because of high carbonates in the water (very common) or because of something the water company adds to the water (also very common). Get a water quality report from the water company. GH and KH are likely reported as something else, but look for anything that is reported as 'ppm CaCO3', Ca, Mg, Carbonates, Alkalinity, Permanent Hardness, Temporary hardness or a few others. Make sure to post the units, too, these can be ppm, mg/l, dKH, dGH or a few others.
Run this test:
Go buy some RO water from a store (gallon jug is fine).
Blend RO + tap in several jars.
25% RO + 75% tap
75% RO + 25% tap
Test GH, KH, pH, TDS
If none of these are what you are looking for make your own blend and test.
Then, starting with the recipe that is closest add a handful of peat moss to the jar. (a tablespoon or so to a cup of water). Stir and test at 24 hours and 48 hours. GH, KH, pH, TDS.
The test results you are looking for:
Neons and many other soft water fish:
GH between 3-5 German degrees of hardness.
KH within a degree or so of the GH.
pH on the acidic side of neutral, pretty much anywhere in the 6s is fine, about 6.5-6.8 would be great, but pH is the least important of these, so do not worry if it is not quite there.
If this test works:
1) Fill the tank with the recipe, a blend of RO and tap that has been stirred or passed through peat moss. (I use a fountain pump and peat moss in a nylon stocking)
2) Prepare the water like this for every water change.
3) Top off with pure RO.