High calcium and alkalinity

[Pas]

Hi to everyone
Am new to this forum
I have a 75 gallon tank and 15 sump that is up and running for two years with only fish and recently been having a tentation to put corals,
I just finished doing a water change, I after finish did a test with API reef master test kit
And
Ph 8.3
Calcium 26 drops = 520 ppm
Kh 11 drops = 196.9 ppm

And just doing every week a 5 gallon water change with instant ocean
Am I doing something wrong?

Am looking for some guidance

Thank you

 

[Dxpert]

How old is your test kit?

 

[Best Fish-Jake]

What kind of salt are you using? I assume your not dosing.. what's your water source?

 

[Pas]

Test kit is around 8 months old with expiration date of 4/18
And salt that am using is instant ocean, not dosing I want to calibrate everything first, water ro/di from municipal water lines.
I check the water again today in morning the kh is the same 11 drops or 196.9 and calcium drop or i just couldn't tell the difference by the lights now is 24 drops 480.

 

[Bacon505]

Its fine, dont beat yourself over it. It will slowly decline over time. If you dont have corals then the depletion will be slower and wc will even slown down the process if you are using high alk cal salt. Its the drastic jump that will kill your corals ex.from 11-7dkh. Calcium is more forgiving