Why Does My pH Have Such A Wide Swing?

[Anonymous]

My pH at it's peak varies between 8.12 and 8.17 per Octopus controller. I am perfectly happy in that range. But after lights out it takes a major dive. Usually I am in the 7.77-7.85 area. When the MHs come in the the morning it's like someone stepped on the gas pedal. It has been this way for about seven months, starting when I began using a calcium reactor. I have followed all of the posts concerning calcium reactor related pH problems and have tried different things including adding a second chamber. My settings are very low- bubble count is 8/minute and drip rate is 50-60/minute I have managed to get the high end up, but my concern has always been the low end and the huge swing which is now even wider.

On the positive side all my corals have never looked better, and I see no difference in them even in the 7.7s. Lots of growth in soft, hard and stonies. Even that weed they call Xenia pulses out of control at the low end. (It could crash if it wants to.)

I really don't want to artifically prop up my pH, but I sure would have a little more peace of mind if I could see less of a drop. I don't have the space for a lighted refugium or I would go that route. Would adding light to my sump be enough help to be worth it? Can the reactor be shut down at night and the tank still maintain proper alk and calcium? Am I headed for long term problems?

My tank including sump is about 140 gallons. Thanks.

[This message has been edited by XXX (edited 06 March 2001).]

 

[Anonymous]

Need more info.
Whats your Alk & Ca. Do you drip Kalk? Do you do anything to the reactor effluent before it goes back into the system. Do you have lots of algae (micro or macro). Have you tested for magnesium, do you do water changes. have you tried taking a jar of water when the Ph is at it's lowest, shake it like crazy for a few minutes, then test the Ph? If so, you've got CO2 buildup.

Let us know

 

[Anonymous]

Bdynes,

Thanks for the response. Alk is always in the 9-10dKH range. Effluent alk is 34dKH. Calcium is 410.

I do not drip Kalk but have given it some thought lately. I would prefer not to but certainly would if need be.

Concerning the reactor effluent, if you mean do I drip it into a dish with an airstone or something to that effect, no I don't. My effluent line is about 3-4 inches above the sump level and drips at the top of the skimmer pump. I've never been convinced that was any help.

My tang makes sure I have little to no macro in the tank, and micro is limited to an occasional dusting of the glass. Coralline growth is good. I do have some algae growth in my overflow but am unsure if it is enough to help. If I pulled it all out it would be about a cup full. This is why I wish I had the space for a refugium.

I do a 15-17 gallon water change every 10 days. Never checked for magnesium. How is that related to this situation? I have never done the shake test. I will today.

Thanks for your help.

 

[Anonymous]

All I can say is don't go chasing the numbers. If everything looks good, and the Carbonate Hardness is where is should be (Alkalinity has little to do with buffering ability!) then its fine. Don't try to fix what isn't broken. People often make the mistake of looking at the numbers and not "listening" to the tank. If it looks healthy, and things are growing, don't change anything.

-Perry

 

[Anonymous]

Perry,

I have always preached the same sermon as you, but I started getting concerned when my low went lower and my high went higher. It began this after switching from PCs to MHs and adding a second reactor chamber. Plus the rapid rise after lights on worried me, allthough it doesn't seem to bother any of the animals. For example. today in seven hours my pH has gone from 7.75 to 8.10. It will probably hit 8.15 by evening.

Bdynes,

I did the shake test when the pH was 7.90. It increased to 7.93.

 

[Anonymous]

You could try dripping kalk after lights out to minimize the swing. Just a thought.

------------------
The dyslexic agnostic suffering from insomnia lay awake all night wondering, "Is there a dog?"

 

[Anonymous]

Hi guys,

Just a few comments.

Perry,

I agree with you on the "don't go chasing numbers" issue. However, you said in parenthetic comment that alkalinity has nothing to do with buffer capacity. I think maybe you got a bit confused with the definitions? Alkalinity has everything to do with buffer capacity. In salt water systems, alkalinity and buffer capacity can generally be considered equivalent, though they do have different chemical definitions. The problem is pH is not too strongly related to alkalinity (or buffer capacity) when the influence of dissolved CO2 is involved.

XXX,

I still suspect that dissolved CO2 is the issue, though I doubt the variation you are getting is harmful. I agree the idea of the "shake test" is correct, but I think the methodology can be improved considerably. It sounds to me like the test as described is meant to remove dissolved CO2 from the water, but a sealed jar that could be vigorously shaken keeps the CO2 in contact with the water. A much better approach in my opinion would be to aerate using an air stone for several hours, keeping the container open. Try the test this way, I think you will see a considerable difference.

I'm not sure why adding a second chamber should make your low pH go lower, but adding this chamber should make the high pH go higher.

Finally, when you changed to MH you may have changed the light intensity and boosted the biological activity during the day time which in turn boosted the nightly activity. In theory, this would increse CO2 consumption during the day and increase CO2 evolution during the night.

Good reefing, Mutagen

 

[Anonymous]

One thing that we've not yet touched on is if the probe is good or not. I've just tossed my IKS probe in the bin after 20 months of continuos service - it wasn't accurate anymore.
Try calibrating yours, put the probe back into service, keep the calibration solution the same temp then the following day, pop the probe back into the 2 solutions that you used. If you see a difference in the measured Ph, then you know the probe is dead!!

Mutagen - good point about the shake test. I was told to do the bucket and airstone thing, but didn't have a high CO2 situation and didn't see differences using either test.

XXX - there is a tiny inbalance in your Ca and Alk (using pure chemistry). 410 mg/l of Ca should arise from a dkh of 7. Dkh of 10 should give 430ppm of Ca, but allowing for a few interferences and the less than 100% accuracy of test kits, you should be OK.
When I pushed my Ca, Alk and Ph out of Ionic balance, it made a mess of any coral that was green. I lost my green palythoa, green mushrooms and green button polyps. Everything else made it through reasonably unscathed. Before I did a 90% water change, I had Ph that would not go above 8.05, Alk at 12dkh and Ca that refused to move above 320ppm.

Mg Alk and Ph are linked in some way. If I remember correctly, a long term decline in Mg can cause problems with low Ph. However, if you're doing 10% changes every 10 days, this is unlikely to be the problem.

Personally, I'd build a de-gas chamber for the effluent, or use a solenoid to shut it off at night and drip Kalk instead. On my system, I have alk at about 11 and Ca at 435, My CO2 goes off at midnight and doesn't come on again until 6am. Once or twice a week, I does saturated Kalk for long term Ph maintenance. 2 litres of Kalk raises 160 litres of tank water by 0.05 Ph.

 

[Anonymous]

Bdynes,

What's the equation for finding out what the ratio of alk and Ca++ ought be? Is it always linear? What if you use meq/l units instead of DKh?

-Nathan

[This message has been edited by Nathan (edited 07 March 2001).]

 

[Anonymous]

XXX

I had a the same PH problem as you. The second reactor solution is the right solution. You need to do a few things if you have not already: First off, use Caribsea ARM in the second reactor. It dissolves up to a PH of 7.0. This is important in your case. Then, make sure your PH inside the first reactor is around 6.6 to 6.65. The second reactor will dissolve the majority of CO2. Also, please describe your 2nd reactor chamber. The most effective way is to run water from bottom of the reactor up through the reactor and exit at the top. Once you do these things, your tank PH should not drop so low at night. Mine was dropping to 7.8 or so by early AM and the second reactor resolved it. The trick is managing the PH in the first reactor to as high as a PH level that you can where the media still will dissolve at a efficient enough rate. As an experiment, raise your PH in your first reactor to 7.0 and wait 2 days and watch what happens to your tank PH. I bet it will not go below 8.0. That will show you where the problem lies.

Joe

 

[Anonymous]

What is this second reactor & how does it work? I am using a calcium reactor also and am having ph problems.

 

[Anonymous]

Hi, Joe
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Joe Stiene:
The most effective way is to run water from bottom of the reactor up through the reactor and exit at the top.Joe<HR></BLOCKQUOTE>

Can you explain why this is so? I have wondered about this and haven't been able to learn which way (in at bottom & out at top or vice versa) a single pass secondary reactor chamber should be plumbed and why.

It seems to me that the relative density of the influent and effluent should determine the correct configuration (i.e. if density of effluent is *less* dense than influent, then effluent should exit the top of the chamber).

Are you basing your rule on density?
Thanks,
Brittlestar




[This message has been edited by Brittlestar (edited 07 March 2001).]

 

[Anonymous]

The density of water coming into a CaCO3/CO2 reactor and that exiting will be too close for there to be any density based benefit of upflow vs downflow.

 

[Anonymous]

Thanks, Randy. Good point about the bubbles. Hadn't thought of that.
Brittlestar

 

[Anonymous]

Hi, Randy,

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Randy Holmes-Farley:
The density of water coming into a CaCO3/CO2 reactor and that exiting will be too close for there to be any density based benefit of upflow vs downflow.<HR></BLOCKQUOTE>

So it follows then that the "direction" of flow (i.e. up or down) should be irrelevant?
Thanks,
Brittlestar

 

[Anonymous]

That I don't know. There presumably are engineering reasons for selecting one over the other. Such issues as dealing with trapped bubbles, etc. I've not used or even viewed reactors enough to have an opinion on the best plumbing setup.

------------------
Randy Holmes-Farley

 

[Anonymous]

Hang on, did I miss something? If you put water into the second chamber at the top, it'll trickle down over the media and flow out the bottom....if it goes in the bottom, the chamber fills up and you get a much longer contact time..Thats too obvious - I'll shut up now.

Nathan, I claim no responsibility for understanding Ca and Alk balance, It's all down to Andy H. Check his page here http://www.andy-hipkiss.freeserve.co.uk/ca_&_alkalinity.htm

I learned it all from him - once you use Meq/l and realise what it means, it gets easier.

 

[Anonymous]

Joe,

My second reactor is a Geo. Water enters from the bottom. I am using ARM for the reason you stated. The first chamber uses Corallith media. I have been pressed for time the last few days, but the last time I checked my effluent pH from the second chamber it was 6.65. I was surprise to see it that low. Is it best to raise it by speeding the effluent drip? My experience has been speeding the drip tends to lower the effluent alk under the 32-35 I try to keep it. Is there a way to balance all of this? My bubble rate is only 8/minute, but would slowing it even more be better way to go?
Bdynes,

My probes are 10 months old. I recently calibrated and do so every three months. I will check them again. Between calibrations they tend to creep up some.

 

[Anonymous]

I checked my effluent pH. It is still at 6.65. Effluent alk is 36. Tank calcium has dropped to 380. Looks like I need to speed my reactor up. Tank pH is 7.75. Once the lights come on it will increase very quickly.

 

[Anonymous]

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