Why is my ph high?!

[JMX100]

Im at a loss at whats going on here.. If anyone might have any ideas it would be much appriciated.. This is a 100 litre aquarium thats been going for about 3 years and only had this problem in the last couple months - I havent changed anything ive been doing. When I do my 10% water changes I re-fill with RO water, about 5.5 pH with salty shrimp minerals that give me kh 0, gh 5, pH 6.4, TDS 100. However my pH keeps buffering to 7.2? Every week. I always test the ro water and mixed water before adding it. At one point I even did a 50% change, and the second it had filled up with ph 6.4 water I tested it.. 7.2 it reads on the ph.. I even use specific ro containers for each aquarium in order to minimise parameter offsets.

Im using liquid test kits, always wash them out properly after each use and have even used 3 different test kits, as I wondered if one was playing up, but no.. All say 7.2.

Nothing in the tank should be causing the pH to rise, I use a neutral substrate from JBL, the only rocks im using are lava rock which shouldnt have any effect on pH, and my usual 206 external filter.

The only things that would effect the pH that I know of should be lowering it! Alder cones, cholla wood, catappa, mulberry and guava leaves..

Temperature is at 22 degrees, I do not use any fertilisers or other products alike, and its a well planted tank, mosses and microsorum, nothing unusual.

7.2 may not sound like an issue, but The tank is usually home to my breeding taiwan bee shrimp, which want the pH from 6.0 - 6.6. Ive had to move them. I do know that if I used an active substrate, e.g ada amazonia that this would lower the pH, however I really need to figure out whats causing this pH rise in this particular tank.

Thanks for reading, any help is much appriciated!
- Jason

 

[Delapool]

That's a tough one

have you checked the kh test? Also have you tested tank kh and say tap water kh (just to see if it is working).

 

[JMX100]

That's a tough one

have you checked the kh test? Also have you tested tank kh and say tap water kh (just to see if it is working).

Yes I have thankyou the tank kH is 1 and tap water kH about 13

 

[sinibotia]

Have you tried leaving out a bucket of freshly made RO+ shrimp salts? That way you can see if it's something in the tank.

If your KH is 0 then your water isn't buffered much at all so it could just be changing from that.

 

[JMX100]

Have you tried leaving out a bucket of freshly made RO+ shrimp salts? That way you can see if it's something in the tank.

If your KH is 0 then your water isn't buffered much at all so it could just be changing from that.

I have yes thankyou, the barrels I use get refilled every 2 weeks or so, meaning that the water I use sits for a couple weeks, and the water it is at the correct pH.

Mind if I ask what you mean by your second point about the kH?

 

[sinibotia]

So, the way buffers work is that they stabilize the pH, right? kH measures calcium carbonate which is the major buffer in aquariums. But without a buffer the pH can swing wildly. Typically it swings down and the pH "crashes" at 0 KH. But it could also swing up, which is what it seems to be doing? At 0 KH the slightest thing could screw with your pH.

What's the KH in the tank vs what you're adding?

 

[JMX100]

Ahh yes I see what you mean now, im adding water with a kH 0 and the kH in the tank is 1. But yeah thats what im trying to figure out, what in the world is screwing with my pH? The water I use goes in many of my other aquarims, with very similar setups (for shrimp) and they dont have problems, kH sits happily a 0-1 all the time as does pH at about 6.4.. Its very strange

 

[Delapool]

Just checking but ph always goes to 7.2 week in, week out? How long has it been doing that and I assume you haven't added anything to tank when it started?

Another thought would if you have checked the lava rock for carbonates? It sounds unlikely but secondary carbonates could occur on the rock. But I assume the rock has always been in the tank from the start?

 

[JMX100]

Just checking but ph always goes to 7.2 week in, week out? How long has it been doing that and I assume you haven't added anything to tank when it started?

Another thought would if you have checked the lava rock for carbonates? It sounds unlikely but secondary carbonates could occur on the rock. But I assume the rock has always been in the tank from the start?

Yeah it does, and has been for a couple months now. Nope I didnt add anything, just my normal routine. I havent checked it for carbonates no.. But yeah youre right its been there from the start - its also imbedded into the scape so would be destructive to take out and test unfortunately, I did have that idea

 

[Delapool]

No worries, thought I'd try that one just in case.

I'm actually wondering if there is another buffer in there at work somewhere. It may explain the ph holding so steady. Then I get stuck.

 

[sinibotia]

No worries, thought I'd try that one just in case.

I'm actually wondering if there is another buffer in there at work somewhere. It may explain the ph holding so steady. Then I get stuck.

It has to be another buffer with origins within the tank...

 

[Delapool]

Darn chemistry...

I thought of phosphate buffering (given kh is so low and as you say, ph can swing up) and that not much may be needed.

But when I used these buffers by accident I'm pretty sure I had phosphate readings off the chart and a really quick search is finding the same info. Still if the OP has phosphate readings maybe.

 

[JMX100]

I can test for phosphates on sunday if that helps

 

[Delapool]

Worth a try.

Is there anything different between this tank and your other tanks? It sounded like you had a few going.

 

[Caliban07]

The carbon content in water with lower ph is higher. Try testing the ph in the morning before lights on. You will probably find that the ph is lower. Perhaps the plants are consuming the carbon a few hours after lights on which will naturally raise the ph. This is a naturally occurring process. With a Kh that low you will get much wider swings come lights on and off especially if the tank contains lots of plant mass.


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[Caliban07]

Something like this may occur if there is no buffering capacity.



If your tests are late in the day then your gonna get the ph reading that represents the point at which carbon has been used up and plants that can use bicarbonates inefficiently try to lower ph. The two opposing processes will achieve a particular ph depending many factors which will be different from one tank to another.


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[JMX100]

Sorry its taken a couple days to reply, Ive been having internet issues The phosphate content measures at 0.25

Yes I have 6 at the moment - the only thing thats different between this setup and the other caridina logemanni shrimp setups is the substrate, in the others im using active substrate, this one has neutral sand

 

[JMX100]

Something like this may occur if there is no buffering capacity.

View attachment 282869

If your tests are late in the day then your gonna get the ph reading that represents the point at which carbon has been used up and plants that can use bicarbonates inefficiently try to lower ph. The two opposing processes will achieve a particular ph depending many factors which will be different from one tank to another.


Sent from my iPhone using Aquarium Advice

Thanks for your help, i'll test the pH in the morning and see if its different

 

[JMX100]

Thanks for your help, i'll test the pH in the morning and see if its different

Hi again, ive been testing in the morning and evening over the past days, in the evening its 7.2 and in the morning its 7.0

 

[Delapool]

So not a phosphate issue and not natural ph variation with day/night it sounds?.

Is kh the same in the other tanks as well? You mentioned 0 to 1.