Saltwater Tank PH is extremely high 8.91

larry reed · Mar 30, 2016

I started a 15 gallon saltwater tank about 4 months ago. Everything was going great, I had corals, fish, crabs and the PH climbed slowly to 8.91 and killed everything. Did real seawater changes with real filtered seawater and the PH came down some but went right back up. I have a 10 gallon refugium and a wet/dry filter for a 70 gallon, along with a protein skimmer & a canister filter. Is it possible that I cleaned my tank filters too much that it caused the PH to go up extremely high and if so, will it re-cycle itself again? If the tank is re-cycling do I need to do the following:
1. turn the lights on?
2. Do I need to add fish again?
Will re-cycling my tank again bring down the PH?
Any suggestions would be appreciated, I need help?

Randy Holmes-Farley · Mar 30, 2016

U less you added some alkalinity supplementing chemicals, the pH didn't just rise on its own.

How are you measuring pH? It is likely an error.

larry reed · Mar 31, 2016

Randy Holmes-Farley said:
U less you added some alkalinity supplementing chemicals, the pH didn't just rise on its own.

How are you measuring pH? It is likely an error.

larry reed · Mar 31, 2016

Randy Holmes-Farley said:
U less you added some alkalinity supplementing chemicals, the pH didn't just rise on its own.

How are you measuring pH? It is likely an error.

pinpoint ph controller calibrated double checked . but if i did add to much alkalinity wouldn't it go down after water change's ?

Randy Holmes-Farley · Mar 31, 2016

larry reed said:
pinpoint ph controller calibrated double checked . but if i did add to much alkalinity wouldn't it go down after water change's ?

Depends on the size of the change. A 10 or 20% change wouldn't do much (a 20% change with 11 dKH water drops 20 dKH tank water to 18.2 dKH), but many changes or bigger changes will.

That said, pH 8.9 won't be stable, especially with elevated alk. The tank generally turns milky white with precipitated calcium carbonate, and if that does not happen, the pH is likely not that high.