Phosguard (alumina oxide) and its effect on pH

aereaus · May 3, 2016

Recently, i set up a media reactor on a 35g nano and loaded it with a half dose of extruded carbon and the recommended dosage of phosguard. Over the course of a week I noticed the pH had dropped from 8.4 to about 7.9, worried i began testing alkalinity daily. I dose alk buffer in my top off so it usually stays stable and over the next week alkalinity stayed between 11 and 11.2 dKH while the pH remained at 7.9. I performed my weekly water change as usual with RS coral pro and noticed after doing 10% that the pH had risen to 8.2 (RSCP mixes to about 8.4.) However, within 2 days the pH was back to 7.9 last night I removed the phosguard from the reactor and am now waiting to see if there is any impact. Just curious as to if anyone else has had a similar experience or what they think the causes may be.

Thanks in advance and happy reefing.

Randy Holmes-Farley · May 3, 2016

There should not be any ongoing significant impact of Phosguard on pH. Reduced phosphate may somewhat increase the demand for calcium and alkalinity, but I suspect the pH effects you are seeing are either a one time effect or are coincidence.

aereaus · May 3, 2016

I suspect you are right I am just very confused as to what is causing my issue the only other relevant fact is that I removed some chaeto from the refugium everything else has stayed the same

aereaus · May 3, 2016

Randy Holmes-Farley said:
There should not be any ongoing significant impact of Phosguard on pH. Reduced phosphate may somewhat increase the demand for calcium and alkalinity, but I suspect the pH effects you are seeing are either a one time effect or are coincidence.

Just tested pH, 16 hours after removing phosguard (no other changes) pH has risen to 8.4, i suspect had I left it in it probably would have eventually normalized and maybe this is some weird coincidence but I plan to wait a week to see if the pH stays at 8.4 -- if so I will add a half dose of phosguard back to the reactor and see if there is any impact. I am legitimately curious now.