pH At 9!

[BigEZ77]

Previously I was using the API test for pH and it was reading an acceptable 8.2-8.4. I recently purchased the Milwaukee pH Tester, calibrated it this morning and its reading 9! My phos and nitrate are undetectable but I've been experiencing a diatom bloom for 3 weeks now, so I understand they may not be accurate. My cal is 420, alk 11.2 and mag 1400. Any ideas on how to lower the pH or do you think there could be something wrong with the tester?

Thanks,

[GimpyFin]

It's possible the tester calibration is off, not sure. Milwaukees test equipment is pretty solid. High pH can be a lack of carbon dioxide. Your alk is 11.2, alkalinity buffering could deplete this causing a rise in pH. If it were me, I'd slowly let alkalinity drop to around 8 and see where you're at.

[Sk8r]

Water changes are also good.

[BigEZ77]

I do a 10% per week and did one each day from Fri-Sun due to the diatom bloom. How to I let the alkalinity drop? I'm using Instant Ocean and not dosing anything.

[Dkuhlmann]

PH and Alk are tied together, if one is high so will the other one be high. This is what you're seeing. Your Alk at 11.2 is very high, lower the Alk to 8.5 and see what your PH reads.

[BigEZ77]

Thanks. So how do I lower Alk? Change my salt mix to something that has lower Alk or is there something else I can do?

[disc1]

Originally Posted by Dkuhlmann

PH and Alk are tied together, if one is high so will the other one be high

That's not quite true. I can have high pH and low alk or vice versa. The two do work together, but they don't necessarily track one another. You also have to consider the CO2. Those three must maintain a mathematical relationship.

[jason2459]

Agree, my pH is normally rather low to very low but it's easy for my alk to be too high to very high if I'm not careful.

My house is closed up pretty much year round due to all sorts of allergies. This drives down my pH to 7.8 or lower with no intervention. Especially in the winter when the furnace is running and fireplace at times.

My alk normally runs around 8-10 with zero intervention and with Kalk additions it will easily hit over 11 if I'm not careful while pH will be around 8.0.

Heck, I had an issue around a month ago that drove my alk to 14 but my pH barely broke 8.2.

So, not everyone can ignore pH and just watch their alk.

[disc1]

Originally Posted by jason2459

So, not everyone can ignore pH and just watch their alk.

It's not that alk would tell you that the pH is OK, it's that the pH isn't really that important of a parameter in the big picture. As low as 7.8 and things grow fine. Much lower than that and the sand starts to dissolve and that drives it up. Up to about 8.6 it's fine. Much above that and you start to get a little precipitation which drives it down. It's pretty hard to get a reef tank way out of pH range. We run a pretty tight range of only about 1pH unit and it's pretty hard to get outside of that without something else being really out of whack.

Where pH becomes critical is in freshwater tanks with little or no buffering capacity. There the pH can range from the high 4's to the low 10's depending on what's going on. And those fish all tolerate differing ranges so what works for african rift fish won't work for amazonian fish and so on.

[jason2459]

Yes, I've had issues with sand before. pH is an issue for some people and I'm one of them. Luckily I've had access to resources like reefcentral and posters like you among many others with considerable knowledge that has allowed me to understand those issues and how to help correct them.