Cannot get my pH to stay up

[klikini]

Hi everyone,

I have a 20 gallon long that is 3 years old and has been perfectly fine up until the past month or two, when the pH dropped to 6 and got stuck there. It might actually be a little below 6 (the minimum pH of the API test), so I got some pH test strips that go down to 1 and they showed it around 5 or 6 (hard to tell exactly due to the wide pH range but limited color range of the test).

After talking to my LFS about it (and a lot of moral reflection), I decided I would like to add a blue ram to help cull the platy population. However, they recommended I get my pH higher first, so that's what I'm determined to do.

Now, I've read dozens of times during my research lately than chasing pH is bad, but I've only ever seen it in response to (what I consider) perfectly accepting pH values around 7–8 and never anything this low. I am hesitant to add "pH up!" chemicals as I don't think they will solve the root cause, and the low pH will just return later and provide another shock to the fish.

I have successfully raised the GH from 1 to 8 using Seachem Equilibrium (and some crushed coral), but I can't seem to get the KH to increase at all (it turns orange with the first drop!). This seems weird to me because in my other tank (a 5.5 gallon shrimp-only tank), the KH is 4 and the GH is 6, and they fluctuate more or less in sync with each other.

What I've tried:

• 25% water change, twice a week, for the last 2 weeks. It doesn't make much of a difference in the hours and days following even though the tap water pH is 8.2 (also measured with the API kit).
• Adding crushed coral, per the recommendation of my LFS. It raised the GH a bit but didn't change the pH. I also had some trouble getting it to dissolve even after 2 weeks and moving it from the substrate to the HOB filter for more water flow.
• Adding Seachem Equilibrium. I was previously in the habit of doing this with each water change but stopped about a year ago, until this week. This also raised the GH significantly, but not the KH or pH.
• Removing 90% of the live plants, as my LFS identified this as a possible cause of the low pH. No change in pH.
• Turning off the CO₂ completely for a week. No change in pH, so I have re-enabled the timer.

Tank setup:

• AquaClear 50 HOB filter
• Two 50 W heaters each preset at 78°
• Light on for 8 hours a day
• CO₂ around 1 bubble per second while the light is on (it's planted tank; see attached photo)
• Bubble bar for more water oxygenation

Current tank inhabitants:

• Approximately 3 adult platys.
• Approximately 5–10 juvenile platys.
  • A couple of them seem deformed and unable to move very well, but they still eat whatever food falls near the substrate. They were fine until recently, and they do better immediately following a water change, so I don't think it's inbreeding, just the pH messing them up, but I could be wrong.
• Approximately 20–50 baby platys, some barely big enough to see.
• 1 cory catfish
  • The other very sadly died a few days ago, I think as a result of the pH drop.
  • I know you're supposed to have more than that (and I used to!) but I've had a difficult time finding healthy ones in stores around here.
• Uncountable number of bladder and ramshorn snails.
• Occasionally I will see a blue shrimp (neo.), but it's been a while, so he may have finally died of old age since he was a very early addition to the tank.

Water parameters, all measured with API liquid tests:

pH (tap water)	8.2
pH (tank water)	6
Ammonia	0 ppm
Nitrite	0 ppm
Nitrate	0 ppm
KH	<1° (<18 ppm)
GH	8° (143 ppm)

Is there anything else I can try to fix this?

Am I correct in assuming the pH shock is what killed the other cory and is causing problems for the juvenile platys?

Thanks,
— Andy

 

[Andy Sager]

I would think the CO2 is your main culprit to your low pH. You more than likely have poor exchange of gases at the surface if you are using CO2. I'd turn off the CO2 and increase aeration in the tank and see if you don't get a higher pH within a few hours to a day. Just turning off the CO2 will not change pH. You need to add aeration to get the CO2 out of the water.
The low KH also doesn't help to maintain a higher pH. If the crushed coral isn't working, you might try adding a cuttle bone to the filter so the the water passes over it just before it returns to the tank. ( Speaking of which, what kind of filtration do you have for this tank? )

If all else fails, since your tap water's pH is that high, you can do daily small water changes to help bring the pH up. The closer to the tap's pH you get the larger amount of water you can change with little effect on the fish. Getting the pH up is just one part of the issue. You'll need to fix the kH to keep it higher.

Hope this helps.

 

[Aiken Drum]

Is there a difference between your pH when the lights and CO2 are on, and night when the lights and CO2 are off and the CO2 has had chance to offgas?

While this may not be related to your pH problem, it looks like you have your bubbler turned on. You want the airstone off while the CO2 is turned on, otherwise the CO2 just offgasses and you get no benefit. During these periods high demand plants that utilise the CO2 will be supplying the O2 needs of your fish. At night, when the CO2 is off and the plants arent photosynthesising, that's when the bubbles should be on to oxygenate the water at night.

Are any of your plants high demand species? None of the plants I can identify in the photo really need injected CO2. You need the high demand plants along with high light and nutrient dosing when using CO2 so they produce the O2. If your plants don't need the injection CO2, then as @Andy Sager suggests, it will be lowering your pH with no benefit. Also if your pH is down to your CO2 rather than mineral content (or lack of mineral content) then it's less of a concern for fish. Measure your pH when the CO2 isn't running, and that's what you should consider your waters real pH.

 

[klikini]

I would think the CO2 is your main culprit to your low pH. You more than likely have poor exchange of gases at the surface if you are using CO2. I'd turn off the CO2 and increase aeration in the tank and see if you don't get a higher pH within a few hours to a day. Just turning off the CO2 will not change pH. You need to add aeration to get the CO2 out of the water.
The low KH also doesn't help to maintain a higher pH. If the crushed coral isn't working, you might try adding a cuttle bone to the filter so the the water passes over it just before it returns to the tank. ( Speaking of which, what kind of filtration do you have for this tank? )

If all else fails, since your tap water's pH is that high, you can do daily small water changes to help bring the pH up. The closer to the tap's pH you get the larger amount of water you can change with little effect on the fish. Getting the pH up is just one part of the issue. You'll need to fix the kH to keep it higher.

Hope this helps.

I forgot to mention it, but I did turn up the airflow to the bubble bars when I disabled the CO₂ timer.

Thank you for the cuttlebone idea! I bought one and put it right before the outflow from the filter (AquaClear 50 HOB). I'll check how much has dissolved and measure the pH again in a few days and report back.

 

[klikini]

Is there a difference between your pH when the lights and CO2 are on, and night when the lights and CO2 are off and the CO2 has had chance to offgas?

While this may not be related to your pH problem, it looks like you have your bubbler turned on. You want the airstone off while the CO2 is turned on, otherwise the CO2 just offgasses and you get no benefit. During these periods high demand plants that utilise the CO2 will be supplying the O2 needs of your fish. At night, when the CO2 is off and the plants arent photosynthesising, that's when the bubbles should be on to oxygenate the water at night.

Are any of your plants high demand species? None of the plants I can identify in the photo really need injected CO2. You need the high demand plants along with high light and nutrient dosing when using CO2 so they produce the O2. If your plants don't need the injection CO2, then as @Andy Sager suggests, it will be lowering your pH with no benefit. Also if your pH is down to your CO2 rather than mineral content (or lack of mineral content) then it's less of a concern for fish. Measure your pH when the CO2 isn't running, and that's what you should consider your waters real pH.

You might very well have a point about the lack of high-demand plants. I've taken out of a ton of plants chasing this issue, and I've also gotten rid of some types of plants entirely over the last couple years, so it's very possible I need to re-evaluate my need for CO₂. Right now in the tank there is:

• Madagascar lace
• Cryptocoryne
• Subwassertang
• Mystery plant I got by accident so I don't know the name of (help with identification greatly appreciated; photo attached)
• Christmas moss
• Frogbit

I do think the madagascar lace might be using up a decent amount of CO₂, although I turned it down from 2–3 bubbles per second to around 4 seconds per bubble when I removed the plants a week or two ago.

I have checked the pH at various times of the day, and while it fluctuates a little (the strips show a slightly higher pH at night when the CO₂ is off), there's not a huge difference; maybe slightly under 6 during the day and slightly over 6 at night. I have been only testing the nighttime/CO₂-off pH with the wide-range/low-precision test strips and not the API liquid test, so I will test it with the liquid test later tonight once it's been off for a few more hours and report back.

 

[klikini]

Update: I tested the pH using the API kit after ~4.5 hours with the CO₂ off and with the bubble bar air valves open all the way, and it was only up to 6.2.

I also recently read in another thread here that you should let tap water sit out for a while before testing its pH, which I did not know or do to arrive at my previous measurement of 8.2, so now I have some sitting in a beaker overnight to test tomorrow.

 

[Andy Sager]

Update: I tested the pH using the API kit after ~4.5 hours with the CO₂ off and with the bubble bar air valves open all the way, and it was only up to 6.2.

I also recently read in another thread here that you should let tap water sit out for a while before testing its pH, which I did not know or do to arrive at my previous measurement of 8.2, so now I have some sitting in a beaker overnight to test tomorrow.

That's correct. You need to let the tap water " gas off" to get a more actual pH level. As for raising the pH, you don't want to do it rapidly as that can adversely effect fish.

 

[klikini]

After a week with the cuttlebone at the HOB outflow, my new parameters are:

pH (tap water)	7.2
pH (tank water)	6.5
KH	2°
GH	8°

It seems to have raised the KH and pH a noticeable amount, so I'm hopeful that this will continue slowly the next few weeks. Thanks for the help!

 

[Aiken Drum]

Is that when the CO2 is running or when it's switched off?

Injected CO2 when working properly should be causing a drop of around 1 pH compared to when it's not running.

 

[klikini]

That was measured about 3 hours after the CO₂ turned off.

I only see about a 0.5 pH fluctuation based on the CO₂ being on or off. Maybe because I'm running so little of it since I'm trying to reduce swings right now?

 

[Aiken Drum]

Either run the CO2 properly or just turn it off. In your case, turn it off. Which I'll come to later.

pH swings arent necessarily a problem. It's the cause of the pH swings that might be. Fish go from one pH to another quite readily. Anyone who runs CO2 will tell you that, and even without CO2 you might find pH is different at various depths and times of the day.

It's swings in disolved mineral content that fish don't tolerate, and the disolved mineral content causes pH levels. Most people have pH tests rather than total disolved minerals (TDS) tests, so its the pH swing that they notice, but its not actually pH that fish reacting to.

pH swings caused by disolved gas content aren't a problem.

There is a relationship between pH, KH and CO2 such that if you know 2 you can calculate the 3rd or look it up on a table. The table assumes there is nothing else effecting pH other than KH and CO2, which isnt normally true, but its still a useful guide to how all 3 parameters interact with each other.



What you can see from the table is your CO2 levels are in the green without the injected CO2. From what you say if running CO2 is causing a 0.5 pH drop to below 6 then there is too much CO2 which is a dangerous level for your fish.

Do you have a CO2 drop indicator checker? An indicator will give you your CO2 levels without relying on interpretation of other parameters and tell you if you have sufficient CO2 levels for your plants or too much for your fish. If you are actively injecting CO2, it's an important tool.

 

[klikini]

I do have a drop indicator. I just replaced the solution (4 dKH) today and even after running CO₂ for 4 hours, it was still pretty blue (photo attached).

I don't have a printed color reference chart but from what I can find online, it appears to be in the 3-5 ppm CO₂ range. That might explain why my madagascar lace is unhappy lately...

The new solution didn't get much time with the CO₂ turned on today, so I'll report back tomorrow if I notice any change in color.