pH issue - please help!

Hi,

I've got a pH problem that I cannot solve - is there anybody here willing to help?

I was using 2 days old tap water in the beginning, but my pH once balanced would grow by 1 in half a day.
I had decided to change to demineralised water, but when I was filling my res for the first time I have lowered pH too much and added some tap water to bring it back to 5.8
I did the water change at noon and at midnight it was 7!
I changed water again, this time I managed to balance it to 5,8 after adding nutes.
guess what?
I just checked the pH and it was 6,9 now after only 9 hours!!!

I am using GRODAN rockwool as a medium, GHE TOTAL GRO, GHE BIO ROOTS, and GHE pH DOWN buffer.

I brushed the res before changing water,

oh - I germinated plants in rockwool using tap water - do you think that this could be influencing the pH until now?

Please help - I am planning to be leaving for 3-4 days several times soon - I have to do something about it!

Adam

Hi Adam,

Do you know that rock wool is high in pH and you are suppose to soak them overnight in pH 5.5 water before using?

Lets suppose you did. do you know that tap water set out for a few nights will remove the chlorine but not the minerals? If your in dirt it should be OK but if your hydro you got problems and need fresh water like r/o or distilled.

Every time you water you run the water through the growing medium and the pH could change. The best way to avoid this is to use a larger res so the change wont be so high.

Maybe that will help.