texas holey rock alkalinity

[SDchris]

I have 7kg of texas holey rock (nothing else) in a 120L setup. Filled it up with natural seawater and has been running with just the pumps and heaters for the last two weeks.
Tested the water today and alkalinity was 15dKH and calcium was 460ppm. Tested some seawater that was left over from the original batch and it measured 7.3dKH and 410ppm.

Will drain and refill again and see what happens.

Any one else experiance this with holey rock?

Chris

 

[Randy Holmes-Farley Verified Community Expert]

If it is really Texas holey rock, it shouldn't have too much impact as it would be limestone, which generally won't dissolve much in seawater.

However, if it is a replica rock sold for aquarists, it may be like other artificial rocks which will tend to boost pH and alkalintiy due to the cement ingredients in it (particularly calcium oxide, which essentially makes limewater (kalkwasser) and needs a lot of rinsing before aquarium use.