pH has dropped, can't figure out why, is it getting dangerously low?

[Diznaster]

My pH is at 7.6 right now. I'm worried about my fish, no corals yet. The tank is only 63 days old. I have been oscillating between 7.9 and 8.05 (night/day) consistently for a while. Over the last couple days my pH has been trending lower.

I realize from reading the many great articles from Randy that CO2 is the main driver of pH. Thinking about what might have happened mechanically to increase CO2 recently, I did close the basement registers a few days ago, because we switched from heat to AC. But this is an older leaky house and aside from a week of 70's we have had the windows closed for months. I re-opened the registers and basement windows over 12 hours ago and see no change in pH.

KH could be a factor, I am using Red Sea salt which measures 4.0 new (just measured a batch), and my tank had dropped to 3.0 over last month. I wasn't concerned since 3.0 seemed maybe closer to nominal.

All other parameters I can measure are okay: NH3/NH4/NO2/NO3 all zero.

90 gal tank 40 gal sump, plenty of flow/skimmer capacity. I have a big air pump that is meant for power outage (not running skimmer), I turned that on yesterday also and no change.

I'm have been adding a fish per week for the last 4 weeks (5 weeks into cycle when NH3,4/NO2 at zero).

I have also been having the "normal" new tank/new sand/dry rock Diatom bloom, it seems to be slowing down. When doing maintenance I use a canister filter with only mechanical filter (sponge/pads) that I use as a sand vacuum and occasional water polisher. My reasoning is if I brush off the Diatoms from the rock and suck them off the sand into the canister vac it should remove them and the silicates that causes them before they decompose and recycle the problem.

My best is guess some secondary bacteria cycle making more acid. I'm worried that 7.6 pH might harm my fish. What can I do besides water changes to help them if this is dangerous (Soda Ash..?). Any other ideas? What else can I tell you to help you to help me?

 

[11f150]

If the tank is in your basement...thats usually it. I would make sure some fresh air is getting into your basement. I have a similar issue since my tank is in the basement. Fortunately, only half my basement is underground so I have windows/doors that I can open. I always leave a window open now and my ph is fine. It took around a week to stabilize with the window open so if you have one open, I would give it a few days. You can also run a air line for your skimmer outside. Just make sure to read up on that. If you decide to run a air line from outside to your skimmer theres a few key things to remember. If you have to run it far, I would run a 1" pvc pipe from outside to your skimmer and have some carbon in the pvc to protect your tank from outside contaminates like pesticides or fertilizers. Running a bigger pipe to your skimmer lets your skimmer get the same amount of air as if there wasnt a tube on it.

 

[Flippers4pups]

Baked baking soda (soda ash) will only temporarly pull PH up, then it will drop again.

What's your calcium and magnesium levels at?

You could try kalkwasser. Sodium hydroxide in your ATO Reservoir. It can help stabilize and raise PH.

http://reefkeeping.com/issues/2005-01/rhf/index.php#13

 

[Randy Holmes-Farley]

The pH certainly could have dropped, but it’s also worth recalibrating to be sure.

 

[Diznaster]

Unfortunately running a line for outside air is not a reasonable option. Bummer because I could have done it when I finished the basement recently, ran water and drain to closet by tank but didn't know about the need for fresh air until now. Having the window open for a day now (small window somewhat close) pH is up to 7.7. I just took a cup outside and stirred it for 5 minutes and that is up to 8.2 per test kit. I think my probes are OK. I have one in the sump and one in a calcium reactor (which has been CO2 off, I plumbed it in for eventual use but don't need it yet). Both probes agree and followed the same trend. Test kit also corelates.

Flipper: Cal was 450 Mag 1400 a couple days ago, I'll check them again soon. Nothing much to consume it and it seems to not really drop.

I think it's just air, but surprised closing basement registers made that much change. We went straight from winter to summer here so not like we suddenly closed windows. Also have been running stove less and grilling more. If I keep the registers open my basement will be 60 degrees with the AC on, so that wont work. Looks like I'll need a CO2 scrubber. If I use that backup air pump to push air through one, I could program the APEX outlet run it only when pH got to a certain low. I'll have to look into a DIY scrubber, not sure if the BRS one will fit my space. Can't seem to figure out why they say to put a Tablespoon of water in the bottom, otherwise it seems like a tube with fittings and media would be all I need.

 

[Diznaster]

It's been a while since last post and I have been learning and implementing things to reduce CO2. I'm treating this as a degree of effect experiment, basically I want to add/improve practical things I can do to reduce CO2 and increase and stabilize pH. Some of these things are not sustainable, like windows open with a fan come winter time. So at some point I need to turn that variable off and determine the effect.

My pH swings have reduced considerably, my fish seem happier. My "new tank" Diatoms seem to be slowing down considerably and this might be I suspect due to the end of pH dropping to 7.6 and not dissolving the dry rock and releasing more silicates. Please let me know if that assumption seems ignorant or not.

That said here is what I have done so far:
1. Fresh probe calibration on APEX, verified after, did not change a considerable amount
2. Opened basement window and put a powerful fan in it 24/7.
3. Added CO2 scrubber that is being force fed by an air pump to sump.
4. Increased surface agitation in DT and turn hood fans up to ludicrous speed.
5. Turned HVAC system to always run fan when not heating/cooling. I have a return vent near the tank (always open) and several supply registers which are scattered in the basement and currently shut due to not wanting to AC the basement. Opening them in the winter should ideally improve air circulation in basement when windows can't be open. I might try to test this but it is somewhat moot since I cant blow 20F air in house from window for 3-4 months in winter. Upstairs has more air leak paths, so air upstairs should be fresher and winter might be best case with basement supply vents open (I'll soon find out).

So all that said, my diurnal pH swings are almost gone and I even today was able to tell when the oven was on for 3 hours and then off while I was at work by a subtle pH drop of 0.1 and rebound on off . That said my upper pH is still 7.95ish. I suspect some of this might be due to living in a dense city environment, perhaps our CO2 is un-naturally elevated and equilibrium with "fresh" air is at 450ppm CO2?

My biggest question now is:
Assuming I am at general equilibrium to "fresh air" and I only assume this due to relatively low pH swings (under 0.1). I should be able to increase KH and also increase pH. KH is currently at 3.2Meq/L or 9.0dKH. I have a CaCO3/CO2 reactor that I can turn on. I understand this could drop my pH due to the CO2, but assuming I have good gas exchange is it possible that I would see an increase in Ph?

 

[BluTang85]

So I was having a similar prob mine was around 7.8-8.0 and could not get it to 8.1-8.3 and tried everything. My tank is also in the basement. I used this product with 2 doses and it took a few days but my ph raised to 8.15-8.3 and it’s stable along with all my other parameters. I guess it’s worth a try if u have tried everything.

 

[Randy Holmes-Farley]

So I was having a similar prob mine was around 7.8-8.0 and could not get it to 8.1-8.3 and tried everything. My tank is also in the basement. I used this product with 2 doses and it took a few days but my ph raised to 8.15-8.3 and it’s stable along with all my other parameters. I guess it’s worth a try if u have tried everything.

I'm sorry for sounding harsh, but that product is not the best way to raise pH.

All buffers are alkalinity supplements (including that one), and you should never add them unless alkalinity is low.

If you want to raise both pH and alkalinity at the same time, there are more effective solutions that give much more pH boost per unit of alkalinity added. Hydroxide salts give the highest possible boost, followed by carbonate at about half the effect. Bicarbonate and most things called buffers have a very small pH boost to a small pH decline, and are not the best option. The one you picked actually has quite a small pH boost per unit of alkalinity added.

That is easy to get from the pH 8.3 comment they make, which means it is nearly all bicarbonate and a small amount of carbonate to get to pH 8.3.

 

[BluTang85]

I'm sorry for sounding harsh, but that product is not the best way to raise pH.

All buffers are alkalinity supplements (including that one), and you should never add them unless alkalinity is low.

If you want to raise both pH and alkalinity at the same time, there are more effective solutions that give much more pH boost per unit of alkalinity added. Hydroxide salts give the highest possible boost, followed by carbonate at about half the effect. Bicarbonate and most things called buffers have a very small pH boost to a small pH decline, and are not the best option. The one you picked actually has quite a small pH boost per unit of alkalinity added.

That is easy to get from the pH 8.3 comment they make, which means it is nearly all bicarbonate and a small amount of carbonate to get to pH 8.3.

Right right, no I totally understand that’s why I said if he’s tried everything. My experience with it worked nicely all I put
In there was 5 tsp once and this was about a month ago, it took about 3-5 days and my ph came up and has been stable ever since between 8.1-8.3, my alk is 8.5 and hasn’t moved with the Hanna test kit since adding the buffer. Not saying it will work for everyone but hey it’s worth the shot if he’s desperate wanting to raise the ph.

 

[Diznaster]

I'm not desperate yet. I'm actually happy with slowly gaining improvement. Not in a rush and consider/appreciate all advice! Not to be harsh either but my question was not really answered. I'm truly trying to understand the chemistry and I think I'm getting there, but again I could use some input on this question:

If my alk/KH is 3.2Meq/L or 9.0dKH and I raise it via a calcium reactor then am I correct in thinking it would raise my pH. With the obvious caveat that I need a method to get rid of the CO2 acidity via gas exchange with oxygenated air and that all other variables remained constant?

 

[mcarroll]

I think it's just air, but surprised closing basement registers made that much change.

That's 100% if your air exchange into the space AS WELL AS the main supply of fresh air from outside.

HVAC is serious - that's why it works!

 

[Flexin]

There is so much truth in the air exchange. I went on vacation for about two weeks, everything in my house runs the same, a/c etc while I'm gone. My PH jumped .20 the entire time. I was doing the dance, since I could see the jump remotely from my APEX. Once I return, by the end of the day it was down .20 again. I have the tanks in my office on the main floor. If you can get some fresh air in there, that will help. Chasing PH is a heck of thing.

 

[Brew12]

If my alk/KH is 3.2Meq/L or 9.0dKH and I raise it via a calcium reactor then am I correct in thinking it would raise my pH. With the obvious caveat that I need a method to get rid of the CO2 acidity via gas exchange with oxygenated air and that all other variables remained constant?

Raising alkalinity by any means will help raise pH if CO2 is constant. My understanding is that most people who use calcium reactors end up with lower pH even with the higher alk because of that CO2 acidity.

 

[chipmunkofdoom2]

There is so much truth in the air exchange. I went on vacation for about two weeks, everything in my house runs the same, a/c etc while I'm gone. My PH jumped .20 the entire time. I was doing the dance, since I could see the jump remotely from my APEX. Once I return, by the end of the day it was down .20 again. I have the tanks in my office on the main floor. If you can get some fresh air in there, that will help. Chasing PH is a heck of thing.

For this reason, we should really call it "chasing CO2" instead of calling it "chasing pH." At a given carbonate alkalinity level, the only way to increase or decrease pH is to decrease or increase CO2 concentration in and around the tank.

Unless, of course, you dose a hydroxide or carbonate based additive, which will temporarily increase pH. But, that will also raise alkalinity, which may not be desirable. Plus, even these additives increase pH in part because they use CO2 dissolved in the tank water to form bicarbonate.

 

[Brew12]

For this reason, we should really call it "chasing CO2" instead of calling it "chasing pH."

I think it is perfectly fine to chase CO2. If you chase pH by any other method you can cause issues which is why we shouldn't chase it imo.

 

[Randy Holmes-Farley]

For this reason, we should really call it "chasing CO2" instead of calling it "chasing pH." At a given carbonate alkalinity level, the only way to increase or decrease pH is to decrease or increase CO2 concentration in and around the tank.

Unless, of course, you dose a hydroxide or carbonate based additive, which will temporarily increase pH. But, that will also raise alkalinity, which may not be desirable. Plus, even these additives increase pH in part because they use CO2 dissolved in the tank water to form bicarbonate.

Maybe even "controlling CO2" rather than chasing.

 

[Diznaster]

For this reason, we should really call it "chasing CO2" instead of calling it "chasing pH.

It's getting almost ridiculous how I can see a correlation to people in the house/basement and pH. It's like I have a surveillance tool! As I sit here typing and breathing I am lowering my pH, so it seems counter productive to be home! I raised carbonate a bit and now I don't drop below 7.8 anymore, but I am baffled at how anyone can have 8.3 and actually live in the house. Maybe a climate where windows can always be open. I'm running a CO2 scrubber into a diffuser in the sump and the skimmer and I can barely get above 8.05 on a good day. I'm curious exactly how this gas exchange works. I should be getting high oxygen air from the scrubber which looks like boiling bubbles in my sump. Is this being canceled by the rippling water in my display which is pulling high house CO2 air into my water? Is the scrubber just not enough? Anyone ever push compressed oxygen into their tank, would that even help with a house full of CO2?

 

[mcarroll]

I am baffled at how anyone can have 8.3

I've seen very very few tanks that run at that high a pH.

It doesn't take a super-tight house with a CO2 problem per se. I usually doubt pH numbers when I do see em reported that high, BTW.

 

[chipmunkofdoom2]

I should be getting high oxygen air from the scrubber which looks like boiling bubbles in my sump. Is this being canceled by the rippling water in my display which is pulling high house CO2 air into my water? Is the scrubber just not enough? Anyone ever push compressed oxygen into their tank, would that even help with a house full of CO2?

Oxygen and CO2 are not opposites. People tend to think of them as such because respiration uses one and produces the other, but adding oxygen will not "cancel out" or "remove" CO2, and vice versa. In reef aquaria in particular, adding pure oxygen will not affect pH at all. Reducing CO2 by removing it from incoming air and the air around the tank is the only way lower CO2 and increase pH.

 

[Diznaster]

Oxygen and CO2 are not opposites. People tend to think of them as such because respiration uses one and produces the other, but adding oxygen will not "cancel out" or "remove" CO2, and vice versa. In reef aquaria in particular, adding pure oxygen will not affect pH at all. Reducing CO2 by removing it from incoming air and the air around the tank is the only way lower CO2 and increase pH.

Thanks that helps to understand. Your point about air around the tank is where I'm wondering the dynamics especially. So high turbulence at the surface, or in a skimmer, or air stone bubbles, etc... will cause the water to reach an equilibrium with the amount of CO2 in that air source. If in my sump I have a bunch of turbulence in my skimmer with air scrubbed off all CO2 and other than that there is no turbulence in my sump. This should be decreasing CO2 in the sump since the air into the sump has none. Now if in my display tank I have a bunch of surface turbulence but the ambient air is loaded with CO2, then this would be gaining CO2 and then surface turbulence would seem counter productive. Does that seem possible in a broad sense.