10 Gallon Tank Water parameter advise needed

my goal parameters are GH and KH is around 3-6 and ph of 6-7

My tap water parameter is
GH -4
KH -5
pH - 8.1
I tried to do 20% change using my treated water of HCl (which was left for 1day before adding) parameters below:
GH - 4
KH - 2
pH 4.5

After the 20% water change using my treated water , I tested it after several hours
Here are the parameters

GH - 8
KH - 6
pH 7.8

why do you think I got a higher GH and KH when my tap water is ok and my treated water was is also low in gh and kh. Any methods to lower my aquarium water gh kh and pH?
My rocks are ada dragonstone and lava stones

 

Hi

GH and KH both go up in waters that pass limestone and dolomite formations.

Performing an acid test (you have HCL) on dry substrate ..... and the rocks in the back*, will give you the answer, but I think we already know the outcome.

*Looks like "dragon stone". ADA dragon stone is clay-based and won't react to the acid test. For other "dragon stones" this might not be the case.

 

My

Hi

GH and KH both go up in waters that pass limestone and dolomite formations.

Performing an acid test (you have HCL) on dry substrate ..... and the rocks in the back*, will give you the answer, but I think we already know the outcome.

*Looks like "dragon stone". ADA dragon stone is clay-based and won't react to the acid test. For other "dragon stones" this might not be the case.

rocks are ada dragonstone and lava rocks only. I dont know why my gh and kh would rise?

 

I'd test the substrate or perhaps inform us what the substrate is made of.

 

In my experience you do not need to do this mess of lowering pH and chasing numbers, especially if you buy locally. It seems like you already have fish in there so pH must be lowered slowly if you choose to do so. Instead of cutting with acid I would try ro di water but I really don’t think it’s necessary even if pH is 8