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Why is my pH rising?

9K views 32 replies 9 participants last post by  VinceIII 
#1 · (Edited)
What could be causing my pH to suddenly rise? It used to be reliably at 7.5. I admit that I had gotten relaxed about the pH and wasn't testing it as regularly as the other parameters (lesson learned). After a couple of weeks since the last test, I tested it last Friday and found it at 8.3. I did a 40% water change right away, and here's how it has progressed:

Fri evening 8.3 - 40% water change right away
Sat morning 7.5
Sun morning 7.5
Monday evening 8.2

I tested my tap water to see if that's where the change was, but it was at 7.5 as usual. I'm using the API Master Kit and repeated the pH test.

I've had this aquarium since late February, and its parameters have been fairly stable. I made three changes in the last couple of weeks: replaced T8 fixture with Finnex Stingray, added a Top Fin artificial wood decoration, and started using API Leaf Zone per directions (but haven't used it since last Friday's water change).

The aquarium's specs are in my signature line.

The other water parameters are:

ammonia 0
nitrite 0
nitrate 5

I've been dealing with algae, but just by cleaning it out manually during water changes and working with the duration of light.

I'm wondering if the artificial wood decoration is causing the pH to rise, although I thought artificial decorations wouldn't affect the water quality. I'm not sure what else could be raising my pH so fast. I'd appreciate any ideas you have. Thanks!
 
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#2 ·
Hi VinceIII,

Welcome to TPT!

I would suspect the Top Fin artificial wood decoration. Why, it is likely made out of either polyresin (plastic) which may have had calcium carbonate used as a filler or Plaster of Paris and painted or covered with a polyresin (plastic). It may or not have a glaze on the outside (visual areas) but it is likely there are un-glazed areas. Try removing the decoration for a couple of weeks and see if the PH issue disappears. If it does then take it back where you purchased it and tell them it is unsafe for aquarium use.
 
#4 ·
Thanks for the advice. I removed the Top Fin decoration, did another water change, and put the decoration by itself in a bucket of water. I'll test the aquarium and bucket everyday and see what happens.
 
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#6 ·
AWolf, thanks for the tip about temperature. The room where I have the bucket is pretty warm, so the water is probably within a couple of degrees of the tank.

I tested the water when I got home tonight (about 22 hours after last night's water change), and it's at 8.0. Then I tested the water in the bucket with the decoration in it, and it's at 7.5. I tested the tap water next, and it's at 7.5.

I thought it was odd that the pH dropped to 7.5 a day after the last water change, but is at 8.0 a day after this one. 8.0 actually makes more sense, because I'd think a partial water that adds 40% of pH 7.5 water to 60% of pH 8.3 water would yield a pH of about 8.0. Does that sound right?

I'll keep testing the bucket water over the next few days, and I'll check the aquarium water in the morning and evening.

What are my next steps if the pH in the aquarium rises again and the bucket water doesn't?
If in the next few days the bucket water does rise, I assume I should do 25% water changes in the aquarium every few days until the pH is stably back to normal. Should I expect the pH to come down at all on its own?

Thanks again!
 
#14 ·
I thought it was odd that the pH dropped to 7.5 a day after the last water change, but is at 8.0 a day after this one. 8.0 actually makes more sense, because I'd think a partial water that adds 40% of pH 7.5 water to 60% of pH 8.3 water would yield a pH of about 8.0. Does that sound right?


Thanks again!
No, mixing pH 7.5 water with pH 8.3 water doesn't give you the average of those two numbers. Remember pH is a logarithmic value, so 8.5 pH is ten times less than 7.5 ph when you treat it as a concentration of a substance. And, the water is being buffered against changes in pH caused by weak acids or bases, other than carbonates and carbonic acid, so that also affects how the much the mix will change in pH. pH is a complicated variable!
 
#7 ·
Hi VinceIII,

I wouldn't worry about the day to day PH, as I suggested give it a week or so and see what happens. When you test the water in the bucket give it a good 'swish or two' to mix it up before taking your sample. You'll likely have your answer soon.
 
#8 ·
Will do. Thanks for the reminder.
 
#9 ·
You need to worry more about your daily KH readings, once Your KH falls below 4 the PH Rollercoaster starts up. (No fish likes The PH Rollercoaster) I keep my KH at 6-7 and my PH is very stable, All your fish will like you for a stable PH.
 
#10 ·
I got the API KH test today, and my water is at 5 dKH.
 
#11 ·
Hi VinceIII,

dKH@5.0 isn't bad, that is the amount of carbonate hardness in the water although I would have thought it would be lower with a watersoftener system. Did the GH test kit arrive or perish?
 
#12 ·
Roy, was the water softener system from somebody's else's thread? I don't have a water softener system.

I was hoping the LFS would have the GH & KH kit, but they had KH only. I'll look for GH elsewhere. I was relieved to see that my KH level is ok.
 
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#16 ·
I tested the water a few minutes ago, and it's back at 7.5. I did a 25% water change two days ago, because it was at 8.2, which I thought was dangerously high for my betta (what if it started rising from there?). Yesterday, it was at 8.0 or maybe 8.05. That is what I expected to see today, not 7.5. All the other parameters are ideal. Hopefully it'll stabilize now.

I spoke to a knowledgeable person at an LFS, and he thought it was the Leaf Zone. He thought my plants were probably already getting what they needed, and the excess iron was raising my pH. The pH in the bucket with the ornament has been rock solid at 7.5. I know it's too soon to relax or draw any conclusions. I'll continue testing daily.

Even if the ornament turns out to be inert, I'll go with real driftwood instead. 7.5 is at the high end for a betta, so I'd rather have something that brings it down gently.
 
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#17 ·
Roy, when you advised me to not worry about day-to-day pH, were you talking about the bucket with the ornament, the aquarium water, or both? I ask because my aquarium water's pH is back up to 8.2. I don't know if this pH roller coaster is a natural part of the water stabilizing, or if it's something still in the aquarium that has been the problem.

Here is what is still in my aquarium:

- standard aquarium gravel from Petco
- several plants
- moderate algae
- floating thermometer suction-cupped to glass
- heater (store brand with rubber end caps similar to Aqueon's standard heater)
- nano HOB filter

Speaking of the filter, I just remembered that the sponge that's meant to be the mechanical filtration is just starting to deteriorate. Could it be releasing a chemical that's raising the pH?

Thanks again!
 
#18 ·
Hi VinceIII,

So I checked on the ingredients in API Leaf Zone....Potassium Sulfate and ETDA Iron. Potassium sulfate has no effect on PH, it is basically neutral. EDTA Iron on the other hand is an acid with a PH of 3.5 to 5.5. At first I wondered if it is possible that what you are seeing is the PH dropping after dosing the leaf zone and then rising again afterward....but that doesn't make sense because the bucket with the apparently neutral ornament stays at PH=7.5. Your tap water is 7.5. Just about everything in your tank should have no effect on PH with the exception of the gravel. Some colored gravel is made from limestone covered with an epoxy paint. If the paint chips or cracks the limestone can come into contact with the tank water and effect the PH.

Let's try one more thing. Take a glass of water from the tap and measure the PH. Wait 24 hours and test the PH again. Now grab a handful of substrate and add it to the glass. Let's see if it changes or not.

In the meantime quit dosing the Leaf Zone and check your PH every 24 hours and lets see if it changes or not.
 
#19 ·
My pH rises the week after water change because CO2 is bubbled out. There is CO2 in tap water or well water. So the pH is lower after water change, but as CO2 is released, it rises. If you have a filter and/or airstone, this release can happen quickly. My tanks don't have filters, but I do use a bubbler which helps to move the CO2 out of the tank.
 
#20 ·
Thanks, Roy and AWolf.

I tested the aquarium water this morning: 7.5 (down from 8.2 just last night). These swings are frustrating. I also tested this morning's tap water, and it's at 6.4. First time I've seen the tap water at anything other than 7.5. I'll let it sit and will test it again tomorrow. Then I'll try with some gravel.

This morning's unusual tap water result has me thinking that one of my recent water changes might have been with water that was treated differently than usual. If all of this testing points toward inconsistent tap water, would switching to bottled water be the next step? Again, it's only a 5.5 gallon tank.

I last used the Leaf Zone two weeks ago, and it was the second time I used it. I too doubt it has anything to do with these fluctuations. If Leaf Zone had this potential, I'm sure others would have experienced it and there would be mention of it online. I haven't found any such mention. Regardless, I'm not using it any more until I figure out this pH issue.

I also checked reviews for my gravel (Petco Aztec Bronze) and didn't see any claims about it affecting pH.

The bucket in which I'm testing the ornament was filled with 12 cups of fresh tap water, and that has been at 7.5 all week. I'll give it another week.
 
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#21 ·
Thanks, Roy and AWolf.


The bucket in which I'm testing the ornament was filled with 12 cups of fresh tap water, and that has been at 7.5 all week. I'll give it another week.
You could add an airstone to the bucket, and see if the pH goes up. It would be interesting to know. I've never considered the fact that CO2 exists in our tap/wells to the degree that it will cause larger fluctuations in pH. Someone mentioned this in a thread last week, and your thread reminded me.
 
#22 ·
How are you measuring pH? With a test kit, with a pH probe, etc.? Could this actually be a problem with measurement accuracy?

Adding normal amounts of LeafZone won't affect the tank water pH. Remember, pH is a log function, not a linear one. Adding a teaspoon of low pH solution to gallons of water at high pH will have no detectable effect on the water pH. Add to that the fact that the KH/CO2 buffer will resist changes in pH caused by additions of weak acids.
 
#24 ·
After I bought a pH probe I tried to compare it to the API test kit results and I could never get them to match. For me, API reads about .8 lower than the probe. I trust the probe because I calibrated it with known controls and then measured those known samples and got perfect results.

I'd also recommend rinsing your test tube in your tank water sample several times. Don't dry it. Just rinse it in your fish tank water a few times and fill it.
 
#25 ·
Interesting information about the pH probe. I'm not sure what it entails or if it would make sense for my application, but I would be interested to know if my parameters are different from what my test kit is showing. Your suggestion about rinsing the test tube in the tank water makes sense. I'll start doing that.

Could I be seeing the natural diurnal fluctuation from my plants? I apologize for not mentioning this sooner, but I just remembered that I also replaced some plants recently. Over the course of a few weeks, I went from four medium anubias and two java fern to seven hygrophila corymbosa stricta and one medium anubias. Could this new hygrophila grove be causing more diurnal fluctuation than the three anubias and two java fern that it replaced? Is 7.5-ish to 8.1-ish within reason for diurnal fluctuation?

By the way, the pH is back up to 8.1 tonight. I was testing mostly at night and occasionally in the morning, but I'll start testing at both times every day.

I did a search about bottled water and learned why it isn't a good idea. I'll stick with tap water.
 
#26 · (Edited)
At night both plants and fish are respiring, producing CO2 so normally in the morning your pH will have shifted slightly to acidic due to carbonic acid produced from the co2.
AFAICT nothing died so the swings being a "problem" is a bit overstated.. ;)
It is odd that your pH rose above tap. That is a bit unusual unless you have limestone/shells/ ect in the tank. Normal condition is for pH to decrease due to CO2 or Nitrates..
http://www.advancedaquarist.com/2002/5/chemistry

I suppose it is possible that your plants are sucking up so much of the CO2 so to increase the pH during the day..
In which case higher aeration may help control it a bit.
 
#27 ·
At night both plants and fish are respiring, producing CO2 so normally in the morning your pH will have shifted slightly to acidic due to carbonic acid produced from the co2.
That pattern is what I'm seeing, but I don't know if the approximately 0.6 pH shift is excessive and indicates something else.
AFAICT nothing died so the swings being a "problem" is a bit overstated.. ;)
My betta and the plants seem fine, so I too have started wondering how much of a problem this actually is.
It is odd that your pH rose above tap. That is a bit unusual unless you have limestone/shells/ ect in the tank. Normal condition is for pH to decrease due to CO2 or Nitrates..
Chemistry And The Aquarium: The Relationship Between Alkalinity And pH ? Advanced Aquarist | Aquarist Magazine and Blog

I suppose it is possible that your plants are sucking up so much of the CO2 so to increase the pH during the day..
In which case higher aeration may help control it a bit.
The hygrophila started growing new leaves soon after I put it in the tank, so maybe it's experiencing a surge of growth that is causing a higher respiration rate. I'm guessing the diurnal fluctuation wouldn't vary that much, but I don't know.

I started testing a sample of gravel, but then realized I should be testing all of it. That's a much bigger project and leads me to think it would be easier to restart my aquarium (I'd keep the filter media with its live bacteria).
 
#31 ·
I did some research on CO2 options, and liquid carbon is as far as I'm willing to go. Since API products are well stocked at my LFSs, I'd go with API CO2 Booster. The question is, will liquid carbon get my CO2 and keep my pH where it needs to be?

According to a chart I found for estimating CO2, my 5 dKH and 7.5 pH yield 4.7 ppm CO2. Would CO2 Booster be likely to raise my CO2 to 15~20 ppm?

I can also add a piece of driftwood, thus hopefully lowering pH and raising my CO2. If the driftwood were to lower my pH to 7.3 (I have no idea if that's a realistic estimate), that would raise my CO2 before the liquid carbon to 7.5 ppm.

Is there anything else (other than an expensive gas system) that I should consider? I'm home only a couple of hours in the evening and am usually busy on the weekends, so it's important my aquarium be stable and relatively hassle-free. The ease of silk plants keeps tempting me, but I don't want to give up on live plants if a quick, inexpensive fix like liquid carbon and driftwood will get my aquarium where it needs to be without adding complexity.
 
#32 ·
Glut (Seachem Excel or API CO2 Booster) does not lower pH.

CO2 concentration varies during the day cycle in nature. I belive you are driving yourself crazy for nothing.

Driftwood will lower pH over time, as will any organic decomposition (that's where a dirty filter and mulm is not all that bad). Same goes for adding leaf litter to the tank. The issue with organic decomposition is you don't know what else it will affect and it is not easily controllable.

Changes in surface agitation might affect the pH via gas exchange.

Mind posting some pictures of your tank?

If your Betta is ok and your plants are ok, what is the problem?
 
#33 ·
OVT, I know that pH fluctuates according to daily plant respiration, but I was under the impression that a fluctuation of 0.7 was excessive. I was also concerned that the pH was reaching 8.2, which is high for a betta. I wasn't seeing any signs of stress in my betta or plants, but didn't want it to get that far. I'd rather stay within safe parameters than wait for wide fluctuations and high pH to start taking their toll.

I stopped by an LFS today and ran this by the owner. His take was that, although fluctuations of 0.7 aren't considered acceptable, they're very common. He thought the pH reaching 8.2 was a concern.

I'll take out a few of the hygrophila and see how it goes.

I'll post a picture of the tank later today.
 
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