Large(?) pH-swings. How to minimize?

BatmanGefle · May 7, 2018

Hi guys,
my pH goes from a very good 8,30 at day to 7,9-ish during the night and I think that´s quite a large swing, right? I mean, 0.4 over 24h is more than you usually read about? (Ignore the even lower readings from april 30 in the graph; my skimmer was clogged and didn´t ventilate as it should).

A little background;

150G system. dKH=7 and stable.
BK Double Cone 200 skimmer, running at 64%, i.e. 285GPH of CO2-scrubbed air.
two EcoTech VorTech MP40wQD running reefcrest mode at 75%, i.e. 6700GPH. Placed 4 inches below water surface on opposite sides of the tank. Running anti-sync.
small 9G refugium (6% of total volume which I know is very small, but that´s what I had room for. Planning a complete make-over of the sump to make room for a bigger one). Lights on 8pm to 2pm, and growth is very good!
using Triton Balling (NOT Core7) and dosing 10 times/day (170ml/day and steadily rising) . Dosing seven times when main light is on, and three times during the night. Will switch to Core7 when this batch is finished and I guess that the Na2CO3 in Core7 will help rise/stabilize pH if I dose a little more often during nighttime, but that feels like treating the symptom, not the cause.

CO2 in the room is, in my opinion, not excessively high; around 7-800ppm during night (lör = saturday, sön = sunday).

The usual remedy for pH-swings seems to be more surface agitation/ventilation, but shouldn´t my flow and scrubbed skimmer-air be enough to counteract most of the swing? The surface is not a complete mayhem of waves, but it gets plenty of action (the VorTechs are running so high they actually randomly create small air-vortices from the surface)! If needed I guess I can upload a small movie showing the movement when the light comes on...

I like my VorTech-pumps but since they´re rigid, and only flows perpendicular to the glass, it´s hard to make adjustments, like with a Tunze-pump, to make the surface move even more.
Or should I try another mode on the pumps, even if it feels like the result would be minor since the lack of adjustment is still an issue with another mode...
Or should I try something completely different?

I know that chasing pH is not recommended, and I´m not obsessive about it, but a swing as large as this feels like it shouldn´t be left without at least some concern...

Thanks in advance for your input!
//Martin

Jason mack · May 7, 2018

That sounds pretty normal ..I wouldn’t worry too much .. you could try raising your kh too 8 that might help a little ..

BatmanGefle · May 7, 2018

Jason mack said:
That sounds pretty normal ..I wouldn’t worry too much .. you could try raising your kh too 8 that might help a little ..

Yeah, I am slowly increasing kh to 8 but I´m doing it very, very slowly (bad experiences of raising too fast).
Ok, great to know that you think it´s within normal range. A swing between 0.2-0.3 is what you usually read about, and since the pH-scale is logarithmic it felt like a 0.4 is starting to push the limits....

Jason mack · May 7, 2018

I see the same sort of swings in my tank between night and day , I’ve not had any problems yet ... problems come when we start chasing numbers .. if your tank looks happy .. then don’t worry !

Randy Holmes-Farley · May 7, 2018

I don’t think the swing is an issue, but more aeration will reduce it, even eliminate it if aeration is complete. Folks always think they have good aeration, but equilibration of CO2 is far harder than most people assume (without any data).

pdxmonkeyboy · May 7, 2018

there was a recent article where they measured sps growth with fluctuating ph and a rock stable 8.2 ph. The 8.2ph did NOT do well.

Randy Holmes-Farley · May 7, 2018

Brian Bieger said:
there was a recent article where they measured sps growth with fluctuating ph and a rock stable 8.2 ph. The 8.2ph did NOT do well.

Perhaps you saw a different paper, that that was not my recollection of a paper discussed earlier here at Reef2Reef. It showed a daily swing was not worse than a fixed pH, if the fixed pH had the same maximum as the swing. That's an improtant result, but did not show that pH 8.2 was not good.

Here's another paper. Note this natural swing is from about 7.9 to 8.05.

Diel Variability in Seawater pH Relates to Calcification and Benthic Community Structure on Coral Reefs
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0043843

"In general, accretion rates were higher at sites that experienced a greater number of hours at high pH values each day."

"Finally, our data suggest that as coral reef communities begin experiencing a greater daily duration of low pH values as a result of OA, the abundance of calcified organisms and the structural services they provide will likely be compromised in the foreseeable future."

BatmanGefle · May 7, 2018

Jason mack said:
... problems come when we start chasing numbers .. if your tank looks happy .. then don’t worry !

Not measuring anything at all except KH (well, apart from what I can monitor on the Apex that is) since a couple of months, and the tank has never looked better actually!

BatmanGefle · May 7, 2018

Randy Holmes-Farley said:
I don’t think the swing is an issue, but more aeration will reduce it, even eliminate it if aeration is complete. Folks always think they have good aeration, but equilibration of CO2 is far harder than most people assume (without any data).

Is it worth while to make an effort to increase aeration (from the aeration I'm having at the moment) you think? Or is it just a neved-ending chase with little or no gain?

chipmunkofdoom2 · May 7, 2018

BatmanGefle said:
The usual remedy for pH-swings seems to be more surface agitation/ventilation, but shouldn´t my flow and scrubbed skimmer-air be enough to counteract most of the swing?

It depends on the relative CO2 concentration, both in your tank and in your home. All that aeration and surface agitation really does is exchange air between your tank and the surrounding room. If the tank has less CO2 than the surrounding room, surface agitation will actually decrease pH. By incorporating CO2-rich air from the room into the tank, you're mixing CO2 into your tank, which lowers the pH.

On the other hand, if the air around your tank has less CO2 than the air in your tank, aeration will move CO2 from your tank to the surrounding air. This will cause your pH to go up, since the concentration of CO2 mixed in the water will go down. It's worth noting that your tank likely falls into the first scenario I described. Most homes are CO2 rich, and your graph proves this.

You mention you CO2-scrub the air going into your skimmer? How do you do this? Do you pull air from outside your home? Or do you use a soda lime media? Some people suggest reclaiming the air that comes out of the top of your skimmer because it will still be lower in CO2 than the air in your home.

BatmanGefle · May 7, 2018

chipmunkofdoom2 said:
You mention you CO2-scrub the air going into your skimmer? How do you do this? Do you pull air from outside your home? Or do you use a soda lime media?

Soda lime.

BatmanGefle · May 7, 2018

Looking at the graph for the last two days...

Both nights it flatlines at 7.94 at it lowest. Last night it set at exactly 7.94 for five hours (7am to 12am)!
Equilibrium after all? pH 7.94 should mean CO2 in the air at about 700ppm if the chart I found is correct, and that sounds about right..?

Randy Holmes-Farley · May 7, 2018

From a pH swing perspective, I wouldn't necessarily feel the urge to aerate more. It would be nice to know the O2 values also, but those are harder (expensive) to get with substantial accuracy.

BatmanGefle · May 7, 2018

Randy Holmes-Farley said:
From a pH swing perspective, I wouldn't necessarily feel the urge to aerate more. It would be nice to know the O2 values also, but those are harder (expensive) to get with substantial accuracy.

Yeah, it would. I wondered a little about my O2 a while ago, since my orp is on the lower end of what's considered normal (310 to 325), but everyone I talked to agreed that orp is not a good measurement of...well... anything really.

pdxmonkeyboy · May 9, 2018

BatmanGefle said:
Yeah, it would. I wondered a little about my O2 a while ago, since my orp is on the lower end of what's considered normal (310 to 325), but everyone I talked to agreed that orp is not a good measurement of...well... anything really.

a low ORP alarm is a great way to tell you " come home to something dead"

BatmanGefle · May 10, 2018

Brian Bieger said:
a low ORP alarm is a great way to tell you " come home to something dead"

A lower ORP than usual you mean? Like if I suddenly start seeing readings below 300...
But my normal readings of 310-340 doesn't really tell me anything, right?

Randy Holmes-Farley · May 10, 2018

BatmanGefle said:
A lower ORP than usual you mean? Like if I suddenly start seeing readings below 300...
But my normal readings of 310-340 doesn't really tell me anything, right?

That is my conclusion, yes. At least not in terms that suggest an action.

BatmanGefle · May 20, 2018

This thread is going more ORP than pH now, but since it´s my thread I´ll allow it

This is my orp from about a week ago...

...guess when I added six small (3cm) Chromis viridis to my tank? Yep, may 11th. That bio-load of Chromises(?) is really small compared to what I had in the tank before adding them (which was three 10-15cm tangs, one 15 cm fox-face, four 5cm Anthias', one 5cm file-fish and one 6cm copperband).... Still my ORP went from a steady (several weeks) 320 low to a steady (ten days and counting) 310 low.
More dirt in the water, lower ORP - that I can get...but wouldn't it "catch up" as the nitrogen cycle adjusts to the new load..? Or am I not getting what ORP really is? Or is ten days not enough time?
I´m not concerned by this, I´m just trying to understand my tank... 10mV isn´t much, but it´s consistent so I assume something has changed and I want to know what....

Randy Holmes-Farley · May 21, 2018

BatmanGefle said:
This thread is going more ORP than pH now, but since it´s my thread I´ll allow it

This is my orp from about a week ago...

...guess when I added six small (3cm) Chromis viridis to my tank? Yep, may 11th. That bio-load of Chromises(?) is really small compared to what I had in the tank before adding them (which was three 10-15cm tangs, one 15 cm fox-face, four 5cm Anthias', one 5cm file-fish and one 6cm copperband).... Still my ORP went from a steady (several weeks) 320 low to a steady (ten days and counting) 310 low.
More dirt in the water, lower ORP - that I can get...but wouldn't it "catch up" as the nitrogen cycle adjusts to the new load..? Or am I not getting what ORP really is? Or is ten days not enough time?
I´m not concerned by this, I´m just trying to understand my tank... 10mV isn´t much, but it´s consistent so I assume something has changed and I want to know what....

I don't attribute much importance to ORP readings, but the daily swing is reflecting the pH change itself. I'm not sure the ORP change you see May 12 relates to the nitrogen cycle at all, but if you started to feed more, than might do it.

taricha · May 21, 2018

BatmanGefle said:
More dirt in the water, lower ORP - that I can get...but wouldn't it "catch up" as the nitrogen cycle adjusts to the new load..? Or am I not getting what ORP really is? Or is ten days not enough time?
I´m not concerned by this, I´m just trying to understand my tank... 10mV isn´t much, but it´s consistent so I assume something has changed and I want to know what....

This is likely reading more into the graph than is there, but...
Look closely at your graph post-fish. The lows are creeping up, as are the highs. Looks like in 2-3 more weeks, your "after" may match your "before".