PH Drop

[fljones3]

This has probably been asked before but most of the older posts that I have seen dealt with high PH rather than low. My discus are fine, eating well but I noticed some discomfort/stress in doing >40% WC. Anything lower than that, they don't indicate any visible stress. I don't age mainly because I don't have room where my tank is located. It's in my Study, which is basically a converted bedroom. I knew my PH was low in the tank but today I got a Sera PH test which has a broader range for testing. Here are my parameters.

Out of the tap:
PH 7.0
KH 3
GH 3
NO2 0
NO3 <10

Tank
PH 4.5
KH 3
GH 3
NO2 0
NO3 >10 but slightly

I would like to keep the PH higher (around 5.5-6? min). I thought maybe some direction here would help. Barebottom tank, canister filter, two sponge filters. I cannot think of anything that's lowering it. I do have a lot of surface agitation but it has not bother the discus.

Frank

[RogueDiscus]

Hi Frank,
How long after adding the new water did you measure it and get that reading? How often are you changing, how many fish, tank size, etc? I've read here a few times about folks whose local tap water is acidic enough that the local water company adds something like hydrogen peroxide to raise the pH to prevent corrosion in the system. It reacts and neutralizes eventually, lowering the pH again. You should be able to get info on that from your water company. Just a possibility.

[bluelagoon]

How big is the tank?Your water doesn't have a kh high enough to maintain stable ph.The large WC might not be because of the ph swing from low to neutral,rather it might be dissolved gases and little oxygen in the tap water.

[DJW]

It is impossible to have a KH of 3 and a pH of 4.5 at the same time. (Unless you are also injecting a ton of CO2). You really should re-check those test results. The pH is suspect.

[RogueDiscus]

It is impossible to have a KH of 3 and a pH of 4.5 at the same time. (Unless you are also injecting a ton of CO2). You really should re-check those test results. The pH is suspect.

Dan is the expert!

[fljones3]

It is impossible to have a KH of 3 and a pH of 4.5 at the same time. (Unless you are also injecting a ton of CO2). You really should re-check those test results. The pH is suspect.

That's what I thought. However, I have used API, Seachem, and Sera test kits and they are all consistent. The API and Seachem does not go down to 4.5.
I have no plants and no CO2. If I change about 30% of the water, the Seachem registers just under 5.2.

I have been managing this (without knowing the numbers) for about 6 months. This might have been the reason for when I moved to VA. I had discus when I was in OH, having pretty good success even though I did not know what I was doing. No breeding. When I moved I tried to maintain a 6.5'ish PH and it kept crushing. Ultimately I got frustrated and got rid of all my tanks and fish. Then a 10-12 year sabbatical. This time I am more knowledgable (Thanks Al and this forum!) and have not had any crashes (because I did not mess with it).

However, I at least want to know what's happening.

[fljones3]

How big is the tank?Your water doesn't have a kh high enough to maintain stable ph.The large WC might not be because of the ph swing from low to neutral,rather it might be dissolved gases and little oxygen in the tap water.

I have a 75 gallon.

[fljones3]

Hi Frank,
How long after adding the new water did you measure it and get that reading? How often are you changing, how many fish, tank size, etc? I've read here a few times about folks whose local tap water is acidic enough that the local water company adds something like hydrogen peroxide to raise the pH to prevent corrosion in the system. It reacts and neutralizes eventually, lowering the pH again. You should be able to get info on that from your water company. Just a possibility.

I tested the water before my last WC. I typically do a WC averaging at least 5x per week.
75 gallon, 10 discus, 1 bristle nose, and 4 cories. Yes, I know I am overstocked.
I have been surprised upon learning the PH that the bristle nose and Cories are still going strong.

If it is hydrogen peroxide, how do I proceed beside aging?

[DJW]

Well I'm at a loss to explain what you are seeing Frank. To get water down to pH 4.5 you would have to add enough acid to burn through all the buffer until the KH is 0, and then you would have to add even more acid. I use 100% RO with KH=0 and I have to add 3 ml of muriatic acid to get 50 gallons of water that low. A biofilter could do all of that if it had enough time, but the KH would have to be 0 first.

It sounds like the discus are doing well except for something about the water that is causing a problem with large WCs. It might be that ageing is the only way to allow for larger WCs. I have these water barrels in my little fishoffice, its so crowded in here you can hardly get the door open, but I wouldn't be able to function without ageing the water.

At that stocking level you need a lot of water changes, and 5x a week is pretty good although you might need more than 30%, or maybe some crushed coral in the filter to replenish the buffer.

[DJW]

Dan is the expert!

Not an expert, I'm still learning. If I could learn stuff faster than I forget other stuff I'd be getting somewhere.

[fljones3]

Well I'm at a loss to explain what you are seeing Frank. To get water down to pH 4.5 you would have to add enough acid to burn through all the buffer until the KH is 0, and then you would have to add even more acid. I use 100% RO with KH=0 and I have to add 3 ml of muriatic acid to get 50 gallons of water that low. A biofilter could do all of that if it had enough time, but the KH would have to be 0 first.

It sounds like the discus are doing well except for something about the water that is causing a problem with large WCs. It might be that ageing is the only way to allow for larger WCs. I have these water barrels in my little fishoffice, its so crowded in here you can hardly get the door open, but I wouldn't be able to function without ageing the water.

At that stocking level you need a lot of water changes, and 5x a week is pretty good although you might need more than 30%, or maybe some crushed coral in the filter to replenish the buffer.

Thanks for the input Dan. If I raise KH will the PH rise? I am concerned about the crushed coral because I don’t want the PH to bounce around but I do think the discus would do even better at a 5.5-6 PH at least. I just wish I knew the reason.

[fljones3]

How do you do the crushed coral? Where do you get some and how much?

[DJW]

The dilemma is that if you want a stable pH you need buffer in the water, and buffer raises the pH. In a crowded tank like yours its probably better to not care about the higher pH and find a method of buffering the water that works for you. You have fairly soft water and IMO softness is more important than whatever pH it winds up at.

Its been years since I used a dissolving buffer like crushed coral. Most of the time I control the pH with water changes or some tap water rather than adding something, but you could start with about 1/4 to 1/2 cup in a high-flow area like the filter. The trick is to find the right amount. Too much and the KH climbs, not enough and the KH falls. You can do this without measuring the pH. Since your tap water is KH 3 shoot for the amount of coral that keeps the KH around 2 or 3. I think you can get it at Petsmart.

The higher the stocking level the less room for error, which means good size water changes and some buffering. I have not had problems with low pH unless it gets low enough to stall the biofilter, but in your situation a stalled filter could be serious, so I think you are better off with some buffer and a steady pH, even if it goes above 7.

[fljones3]

An update. I added 1/4 tsp of baking soda to the tank this morning. Retook PH and KH after 2-3 hours.

PH 6.4
KH 4-5 (in between colors)

Without any experience in this, that seems pretty water sensitive to me. In doing a water change, would I adjust the soda for the water replacement only?

Now I will do a WC.

[JamesW]

Does your water have phosphate?

As DJW said, it isn't possible to have a KH of 3 and a pH of 4.5. At least for the API test kit the KH solution is a small amount of acid and a pH indicator, the color change, blue to yellow is the same as the normal range pH indicator (i.e. yellow at 6.8). If you are already yellow with that indicator, and add more acid it isn't going to turn blue, and then yellow two drops later.

Can you put an airstone in a bucket of tap water and re-test?

Are you dosing anything?

[fljones3]

Does your water have phosphate?

As DJW said, it isn't possible to have a KH of 3 and a pH of 4.5. At least for the API test kit the KH solution is a small amount of acid and a pH indicator, the color change, blue to yellow is the same as the normal range pH indicator (i.e. yellow at 6.8). If you are already yellow with that indicator, and add more acid it isn't going to turn blue, and then yellow two drops later.

Can you put an airstone in a bucket of tap water and re-test?

Are you dosing anything?

I don't know about phosphate. I have never tested.
I think I will try that - aerate 24 hours and test.

[DJW]

I bet its the KH test that is bad. Are you using a paper strip test for KH? They are notoriously inaccurate.

[fljones3]

I bet its the KH test that is bad. Are you using a paper strip test for KH? They are notoriously inaccurate.

My latest check was with Sera test strips. Been pretty accurate. I will test again this afternoon with API and Sera.

[fljones3]

Both the KH and GH were consistent between the API and Sera strip tests. If anything the API tested a little lower on KH and slightly higher on GH.

The good thing is that the fish are acting normal. They are acting "more normal" with the PH at 6.5.


I bet its the KH test that is bad. Are you using a paper strip test for KH? They are notoriously inaccurate.

[DJW]

An occasional pinch of baking soda is one way to solve the problem. Its easier if you have a pinpoint pH monitor, but they aren't cheap. You glance at the pH and if its getting near 6 you add a pinch of baking soda at the back corner of the tank, and you can see the pH go up within 5 minutes. It doesn't seem to bother the fish but best to do it in small increments.

[bluelagoon]

I have a 125 gal SA tank with 6 red shoulder serverums and 9 geophagus and are big eaters.In order for me to keep decent study ph about 6.4-6.8 in that tank I feed the tank once a day with 1/4 tsp. of backing soda when I do the first feeding.This seems a lot better than letting it drop out of sight with my kit.In another 75 gal tank I have 1/2 cup of crushed coral in a nylon bag in my filter and that works for that tank.My water is soft from the lake and the city uses sodium hydroxide to bring the ph up to 7.4.Not peroxide that was previously mentioned.I need to age my water for large WC's.It depletes quickly because of low carbon hardness (KH).Each time you feed you fish and waste is produced it's using up some of that carbon hardness;that's how you get ph crashes.

[RogueDiscus]

Thanks Mervin. I mentioned the peroxide. I probably remembered that wrong. NaOH makes sense. I think the peroxide is used as a disinfectant sometimes.

[fljones3]

I filled a spare 20 gallon and put in a sponge filter for an acting airstone. Tap PH was 7.0. After 24 hours roughly PH 6.5. Same after roughly 48 hours.
My 75, I have been adding about 1/16 tsp of baking soda in the morning. Same after a 50% WC. PH has been constant at 6.5.

Question is, what's causing the PH drop? Does Ammonia, Nitrite, or Nitrates affect PH? My experience is, no. Prime doesn't. Sponge filters shouldn't. Poly filter pad shouldn't. At a loss here, but something is going on. I am very thankful that the PH is steady at 6.5. It's restoring my beneficial bacteria. WC stress has gone down a lot.

[bluelagoon]

Your water was soft in KH and your water company may added something to bring the ph up so will not corrode metal pipes.KH and PH go hand in hand,so to speak.

[bluelagoon]

Here's a good understanding of PH.https://extension.usu.edu/waterquality/files-ou/Publications/pH.pdf

[DJW]

Question is, what's causing the PH drop?

Do you have city water?

This is from the City of Richmond public utilities website from 2016:

"Over the years, DPU has upgraded its systems to ensure proper chemical doses. There will also be a new calcium hydroxide system going into service in the next two months to better control the pH of the finished water. DPU monitors the pH of the water with online equipment that provides instantaneous results, and also runs tests twice a day to verify proper chemical dosage."

http://cordpu.blogspot.com/2016/02/dpus-role-in-keeping-lead-out.html

Calcium hydroxide raises the pH above 7 and keeps the pH higher in the pipes. Then the pH goes down after the water is exposed to the atmosphere. Increasing pH to prevent lead contamination has become common in cities where they use surface water, which tends to have a lower pH than groundwater.

[fljones3]

Thanks for taking the time to look. I am actually under Chesterfield water system. I am searching their webpage but so far empty. However, it would make sense for them to possibly follow the city of Richmond.

I did find this.
https://www.chesterfield.gov/DocumentCenter/View/909/Water-Quality-Report-PDF?bidId=

[fljones3]

Here's a good understanding of PH.https://extension.usu.edu/waterquality/files-ou/Publications/pH.pdf

Thanks Mervin.

[fljones3]

OK. Finally found a statement.
"The natural water’s pH can vary, so the pH or acidity of the water is controlled at the treatment plant using lime to make sure that corrosion control treatment works properly and the water coming out of your tap is consistent. The pH in our distribution system ranges from 7.0 to 8.0 pH units, which is in the neutral range."

So, lime is added.

[DJW]

Slaked lime is calcium hydroxide, so its the same process as Richmond.

[fljones3]

Thanks Dan, and everyone.

In summary, am I correct with this statement in light of the low KH.
The more surface agitation the quicker the calcium hydroxide is dissipated thereby lowering the PH.