How to combat pH drift

[Nevenka]

Hi there,
I have 135gal tank with clown loaches, zebra loaches, lamb chop rasboras. gold barbs and peppered corrys. My water source is extremely soft (less then 1 KH, GH units) so very prone to sudden pH changes. Although I do routine water changes every 1.5-2 weeks, I still not always catch that sudden pH drop. I've been trying to use small quantities of coral sand in my filter to increase buffering capacity of water, but it stabilizes the pH at ~ 7.2 (I am using a tiny amount, approx 1 teaspoon) and I am noticing that my loaches are not as active at this pH as I've seen them before. I've tried using Seachem Neutral regulator, but it increases phosphates dramatically, and I already have algae in the tank and don't want to promote it even more. Any other suggestions?

[Diana]

Well, you have eliminated the 2 most popular buffers used in aquariums: KH (baking soda, coral sand, limestone...) and phosphates.

Are you noticing problems with your fish when the pH shifts?

If you keep the GH, KH and TDS stable (less than 10% rise or fall with a water change, for example) it should not matter what the pH is, as long as it is somewhere reasonable for the fish you are keeping.
Most soft water fish are fine with a pH from 6.5 to 7.5, and many are OK with a wider range of pH as long as the minerals (GH, KH, TDS) are in the right range. Changes in pH are less important than changes in the mineral levels.

[JonasBygdemo]

I haven't tried it myself, but Waterlife has a pH 6.5 buffer, which buffers the water to 6.5 automatically. With your soft water, it might work.

[chefkeith]

If water changes were done more frequently that would solve most water chemistry and water quality problems. The nitrifying bacteria are probably using up the kH in the water as it's source of carbon.

I'd recommend 20% water changes twice a week or 10% daily water changes.