what’s your pH?

Do you know how low and how high your pH goes?

JFinch has brought up a very good topic because of something he found in a book about Ocean Chemistry. IMO their pH swing range of 8.2 - 8.9 is too high.
I've seen closed systems where it can get down to 7.7 but in the same system it cannot rise to 8.9. A more viable high number in a swinging system is 8.4, though I have heard of 8.6.

Before I started using the groundbreaking(that was 1996) RDP Refugia the pH in my 75 gal went from 7.9 at 5AM and topped off at 8.3 by late morning. That was too wide of a range and it caused ich on damsels and Yellow Tangs died within two weeks, that is until I set up the RDP Refugia. Almost immediately it hovered between a 5AM reading of 8.1 and then rising to 8.3 as I recall .

This is a very important part of aquarium maintenance that I believe every hobbyist should know. There are other options for raising nightime pH other than a RDP refugia. Let's discuss...

What is your pH at about 5AM and how does it increase through the day

Edited by Mark Peterson

Mine is 8.1 with RDP and late morning 8.3

Thanks Mark!  Now I want/need a pH probe and an alkalinity meter?  I just barely get caught up dollar wise to see what I want/need and you bring up something else!

This ought to be a good and informative topic though!

I did all my testing with those dumb kits. If you want to get exact with a dumb kit, go test the water of someone with a fancy probe! Also bring some of your water and test it with their probe! That's how I would calibrate my dumb kit ...if I still did testing, ...which I don't anymore .

BTW, I found that almost as soon as the first light of dawn begins to appear, the algae resumes normal photosythesis and the pH starts to rise, so it's important to test while it's still dark.

I don't want this thread to end, so I'll update my early results.

Here's a table showing my pH swings:

	Alkalinity (meq/l)	AM pH	PM pH	Ä pH
Normal Cycle	3	8.0	8.2	0.2
RDP Cycle	2.8	8.0	8.1	0.1

pH measured at 6am and 9pm.

Clearly the RDP cycle has resulted in a decrease in my pH cycle.  The unexpected (at least to me) result was that it only pinched down on the upper end of the scale.  I can't explain that...

Tonight I'll start moving my alkalinity back up to where I like to keep it (4 meq/l).  I'll update as I go.

Edited by jfinch

7.9 to 8.2

8.3 8.6


I was worried 8.6 was high ...I turned off my Calc reactor to try to bring ph down.
alk is around 11.3
cal around 390

whish i could bring that up


In your opinon leaving reactor on all night is that bad ........

how high of a PH is dangerous?????

Danny, if you want your calcium higher you should add Turbo Calcium.  If your pH is really that high adding more calcium will most likely drive your alkalinity down. 

When was the last time you calibrated your pH meter?  I don't think it's common to have high pH problems when using a reactor.  What Travis is experiencing is more common.  Are you using any other additives (buffers, b-ionic, ect)?  If you haven't calibrated it lately, I'd suggest you do.  Need any buffer solutions?

I would personally be concerned with a pH above 8.5, but how is your tank reacting to it?  The higher the pH the harder it is to keep your calcium and alkalinity levels up.  You get more non-coral growth deposition of CaCO3 then at a lower pH.

So i should leave reactor on add turbo cal.
to rise my cal. and in turn lower my alk.
which will stablize my PH

I don't know .  You've got me stumped.  I was kinda betting on the uncalibrated pH meter .  If your tank look good, I wouldn't worry too much.

As a general rule of thumb:  use turbo calcium or some other CaCl2 product to make changes to calcium levels and use your reactor to maintain (and make changes to) your alkalnity.

What's the pH of the reactor effluent?  How many drops/min?

No but 7.7 is pretty low for a reef. IMO it should have a diurnal (night to day) variance from 8.1 to 8.4 but can be different if coral growth seems okay.

I am worried about rstruhs pH reading. That's too low for any tank at 9PM. When he and I talked recently it appears the flow through the RDP is very low which is not taking advantage of the RDP. But at 9PM the RDP is dark, so that leads us to look for other problems.

In my experience, a tank that is overfed/overstocked and undercirculated (and sometimes underilluminated), will show the kind of problems that Rstruhs is experiencing. I'm not sure which of these conditions exist but if we had an ORP meter that tank would probably be very low, indicating the need for action.

I'm wondering if Rodney would mind if I stopped by tomorrow. I might be able to visit and maybe he would like to come with me to visit Gary Kemp and his 250 with a school of Tangs.