Why Is My Tank Ph Higher Than My Tap Water Ph?

[bigpee]

Hi,

I did my weekly round of tests today and found my tank's pH to be 8.2. Everything is happy so I'm not too worried however out of interest I tested my tap water. This reads 7.4. Why is my tank pH so much higher? In it I have one log, lots of plants, 17 fish and a tetra optimat that I don't use. All other tests show ammonia and nitrites to be zero, with nitrates at 5. I'm using the API freshwater test kit.

Cheers for any help,

Alan

 

[oswoldy]

I THINK it has something to do with your water hardness, bacteria and the fact its been dechlorinated. My tank PH is 7.6 my tap is 7.0 but my water is fairly hard.

Mike

 

[england]

Iam unsure, what substrate doe you have and do you have rocks / beach shells.some things can raise ph

 

[bigpee]

My substrate is standard gravel. The only other item I have is one fist sized rock. Not sure what it is except it is grey and not porous. Here's a picture of the gravel and rock pre water.