Water change and PH?

[Dave001]

Hey Everyone, sorry in advance for the long post. :)

For the last year or so I've been doing my water changes directly from the tap, normally the tap water was around 7.5, and would settle to 7.2, if left over night, even with 50% weekly water changes, the tank has always hovered around 6.9-7.2, so I've never played with the PH at all.

Lately though, with the drought, the PH levels from the tap water are around 8.3, and it settles to 8.0 if left over night. adding this to tank each week is making the tank water swing a fair amount, from 6.9 to 7.9.

Now to make things even harder, I've recently added CO2 to the tank, which has lowered the PH to around 6.3 to 6.4. As you can imagine, doing a 50% water change with water that has a PH of 8.3 is going to make the PH swing all over the place and the fish will not like it.

I attempted to fix this problem by aging the water first and lowering the PH with hydrocloric acid, if I add 10mls of acid to 220l of water, it lowers the PH to 6.7, but by the next day, it's back up to a PH of 8.0.

So my question is, would it be safe to add the acid an hour or so before I fill the tank, or is it necassary to wait 24 hrs, as most people suggest when using hydrochloric acid?

Thanking you,
Dave

[ILLUSN]

G'day Dave,
thats exactly the problem I've been having with my water. there isn't much you can do. you could boil it to remove tempory hardness, i use to do this and it reduced ph from 7.8 to about 7.2, adding HCl has the same effect but I wouldn't put it in unless you'd let it stand o'night. you could age water and filter through peat (should give you 0.3-0.5 drop o'night).

Your CO2 could help you out as it should bring the ph down gradually over time (several hours). if you keep doing changes your tank's ph will adjust gradually and your fish shouldn't mind, if you change 1/2 your water at a ph of 6.5 with water at ph 8.0 your tank should balance out at about 7.2-7.4. you could do a small mid week change as i use to (bout 15-20%) to help keep your water buffered I think your fish will be ok. I've had discus spawn at 7.2 but only intermittantly.

[ILLUSN]

I must also add I've never got wrigglers at 7.2 hence my move to rain water (6.5).

[Dave001]

Thanks for the reply ILLUSN.

I have decided the best thing to do is to lower the PH of the water in the aging drum using CO2. I done a quick test today and found a single DIY CO2 bottle (with a tablespoon of yeast in it) will bring 220 litres of change water down to the same PH as the tank water with in 12 hrs.

Thanks again,
Dave