Ph always rising - but why ?

[daveron]

Hello,

So the problem is, that my pH is always rising and settling in the range of around 6.8, but I fail to understand why and I hope you will clarify the problem for me. Let's get into details:

I am running inert substrate tanks, which have the following parameters: pH 6.7-6.8, GH 5-6, KH 0-1, TDS ~125.

My routine is that I do weekly water changes of around 20%. The water for changes is RO water + salty shrimp GH+ + Azoo Triple Black Water (which is basically a tannins and humic acids extract)+ Azoo Ph Lower, and I usually adjust the pH to around 6.0-6.2 as I want to keep it acidic, but the pH just won't go down lower than 6.7(to be exact - If I would add peat, or a lot of those acids, then sure it would go down lower, but after some time it always comes to it's usual 6.8 range). I also adjust the pH of the top-up water, which is RO + Triple Black Water.

As I am adding a lot of acids into the water I thought the pH should stay acidic, unless there is something that absorbs those acids.

So I did a test - I have prepared my usual bucket of water, re-mineralised it and adjusted pH to below 6.0 and let the bucket be. After around 24 hours I have measured the pH of the water in the bucket and, the pH was back at around 6.6. So it raised a lot. Once again I lowered the pH to below 6.0 using Triple Black Water only, and after another 48 hours the pH was again 6.8.

So why is the pH rising ? I understand that with kH 0 there is nothing to buffer the water, but since I am adding acids into the water and there is nothing that could absorb them what causes the pH to raise ?

Thanks !

[Zoidburg]

It's probably best to stay away from products that raise or lower the pH and get a buffering substrate that can keep the pH lower.

 

Is there a reason you want it lower?

[revolutionhope]

I'm not good with chemistry but I think the pH is rising because there is co2 which is in the form of carbonic acid which is being off-gassed hence the pH rising to its equilibrium which seems to be 6.8. Which is fine for most softwater shrimp I should think?

Edit- doesn't answer the question as to why the pH keeps rising after adding more acid on subsequent occasions though I'm sorry!

[daveron]

Thanks for your responses.

Well the shrimp are doing fine - especially mischlings which are breeding like crazy, however I wanted to lower the pH to suit TB preferences better, and possibly get more breeding.

I am also genuinely interested as to what is causing such pH behaviour.

 

[Zoidburg]

I would say that stability is more important than having exact parameters. Besides, if they are thriving just fine in it the way it is, why change it?

 

What I know for sure is that without KH, the pH can swing and be unstable. Without a buffering substrate, the pH is likely to climb. If you want lower pH, then invest in buffering substrate.

 

Make sure that there's nothing in the aquarium that could cause the pH to rise (such as rocksthat are not inert) and possibly look into driftwood and leaves. Maybe even use peat moss to try and lower the pH naturally.

 

Using the pH down chemicals doesn't result in stable parameters, and I don't think they are meant to. It's more of a temporary fix, if you will, and may cause more stress than needed on the inhabitants.

BTW, if you can get something like the Marina Hang On Breeder Box that uses a small pump to circulate water into the box from the tank, and you modify it to be safe for shrimp, you could put a small layer of buffering substrate into the breeder box. In this way, you wont have to replace the substrate in your tank, but you will still have something to buffer the pH down.

 

The only caution here is that some substrates *will* release ammonia, so you may need to "cycle" the substrate first prior to use... unless you can find one (i.e. SL-Aqua Soil or?) that doesn't release ammonia (or not much at all) that can be used asap.

[daveron]

Pretty awesome tip with that Marina Breeder Box.

I already did something like that in my TB tank, but instead used one basket in my canister filter. I placed around 1kg of H.E.L.P Shrimp Soil in it. Unfortunately It hardly buffered the water any lower. Maybe 1kg is not enough , to buffer 30L tank... 

As for ammonia leaching I assumed that only soils like ADA Amazonia which are full of fertilizers will release ammonia, or is that wrong ?

On the other hand peat gets the pH down easily, but you really need to add very small amounts gradually to avoid pH plummeting down, which is not something you can do easily in a canister.

[Zoidburg]

I don't know if any soils besides ADA Amazonia leach ammonia.

I've heard of people putting peat in a sock near the filter outlet, and others who use peat in a bucket prior to doing water changes.

[Brentwillmers]

On 09/12/2016 at 9:12 AM, revolutionhope said:

I'm not good with chemistry but I think the pH is rising because there is co2 which is in the form of carbonic acid which is being off-gassed hence the pH rising to its equilibrium which seems to be 6.8. Which is fine for most softwater shrimp I should think?

 

Edit- doesn't answer the question as to why the pH keeps rising after adding more acid on subsequent occasions though I'm sorry!
 

 

Sorry I know it's an old thread. But it's pretty spot on. I could go into the full reasoning on it. But carbonic acid is something that gets depleated quickly. A situation is in planted tanks with very touchy plants battle with on a daily basis without the addition of compressed Co2 infusion. Using fulvic acids would help to stabilize PH a bit better. But it has an expiration date and will get depleted too eventually. So a buffering substrate is a far more reliable method (also contains fulvic acids) Another thing why unstable PH is a danger on itself is it being logarithmic so acids or alkaline levels when fluctuating can poison your waters very quickly. A PH of 6 is 10 times more acidic than a PH of 7 and a PH of 5 is a thousand times more acidic than 7. 

You trying to lower your PH to 6.0-6.2 from 6.8 keep in mind to do the change very slowly around 0.2 value per 24hour period if possible to avoid the hash change for shrimp. 

Just my late 2c worth?