Rising GH level

[Valcol]

I have a 105 litre planted tank with co2 injection my water parameters are 6.8 pH 4kh 14gh. The GH has been steadily rising.
I use my own ro/di water remineralised with seachem equilibrium acid and alkaline buffers with doses to achieve 7PH 3-4kh and GH 6-8. However after a few days I end up with the former.
What am I doing wrong. Can anybody help.

 

[Byron]

There is no issue with the pH below 7 (assuming you do not intend hard water fish) but the increasing GH and KH is interesting. I would assume this is due to some delayed reaction of the chemicals. Or, there may bee some calcareous substance in the aquarium that is slowly dissolving calcium/magnesium, such as calcareous rock, or the substrate.

EDIT. Seangee posted something I too had thought of but didn't mention, but it is relevant.

 

[seangee]

What is the problem you are trying to fix by using RO water? If you need to soften your water this is easiest achieved by dilution. Mixing your tap water 50:50 with RO will halve the GH and KH and there is no need to re-mineralise. You can work out your own ratio depending on what you are trying to achieve.

Personally I am not a fan of Seachem's products for this purpose. They want you to buy multiple products and then you need to find the right balance. Good business model but not great for the aquarist.

 

[PheonixKingZ]

There is no issue with the pH below 7

I concur. Why do you think there would be a problem with pH under 7?

 

[Valcol]

Many thanks for your advice. It's not the pH and kh I have i
Its the high gh at 14 I am concerned about. I would like it to be around 6-8 .