PH vs KH

[Gorillastomp]

This weekend, i did add some Sodium Bisulfate into my water to reduce KH from 7 to around what it seems to be 1.5 - 2 from the test kit. MY PH seems to be very low, it's at around 6.4 and did not move from that since 3 days. I know that when the KH is reduced it creates CO2 but i would assume that the CO2 would have gas out after 3 days.

Is this normal to have a low ph like that at 1.5 dkh ? Water is in 5 gal bucket so nothing can alter the PH other than the Sodium Bisulfate.

 

[_Maq_]

pH 6.4 does not fit well with 1.5 °dKH. Your measuring methods probably suffer from significant imprecision.

 

[Gorillastomp]

The ph meter is calibrated, so i will assume that the kh test isnt right and it kinda old too.

I have ordered a better kh tester. I will wait until it arrives to continue this test.

 

[MichaelJ]

Sodium Bisulfate into my water to reduce KH from 7 to around what it seems to be 1.5 - 2

You're adding quite a bit of Sodium (Na) when doing this. By weight Sodium Bisulfate is about 19% Sodium. Off the top of my head, to decrease the KH by 5 degrees (from 7 KH to 2 KH) you would add somewhere around 200 mg/L of NaHSO4 or 40 mg/L Na. Not catastrophic, but worth keeping in mind. The best way to gain control of your KH is to mix in RO or rain water - in your case you would have to use ~70% RO water if your tap is 7 in order to reach 2 KH. Alternatively, a natural way is to filter over peat moss or sphagnum - but wont be very efficient if the starting point is 7 KH unless your using an insane amount and like a black water aquarium 🙂 Of course, you could combine all these approaches and minimize the usage of Sodium Bisulfate.

Cheers,
Michael

 

[John q]

This weekend, i did add some Sodium Bisulfate into my water to reduce KH from 7 to around what it seems to be 1.5 - 2 from the test kit.

I can't help but ask the question as to why you think artificially reducing the kh from 7 to 2 is suddenly going to fix any problems you have with the plants in this tank (I'm assuming you're having problems?). Sure, low kh is better, but reducing the kh and adding lots of sodium? I'm not convinced.
Also I believe you currently target a 1.4 ph drop, whilst life (microbes, fish etc) will continue at a ph of 5, I'm again not sure it's ideal.

Just my thoughts 🫡

 

[MichaelJ]

I'm not convinced.

Right. I'd rather take the higher KH (i.e. higher pH) and feed my plants a little more if I had no other way to lower (control) my KH.

Cheers,
Michael

 

[Gorillastomp]

I can't help but ask the question as to why you think artificially reducing the kh from 7 to 2 is suddenly going to fix any problems you have with the plants in this tank (I'm assuming you're having problems?)

HI @John q, I have a small problem where plants stunts then create healthy shoot from that stunted tip then stunt again etc.. and some plant show that there is a type of deficiency. I don't know if it will fix the problem
or not, but i want to make an experiment in another tank first with the lower KH. Why? My ph at night goes up to 8.3 and i think it may makes the chelated less effective. I could be wrong and have no effect at all but i want to see if the plants may grow healthier that way. Keep in mind i only feed via water column, i don't have an active substrate.

Sure, low kh is better, but reducing the kh and adding lots of sodium? I'm not convinced.

You're adding quite a bit of Sodium (Na) when doing this. By weight Sodium Bisulfate is about 19% Sodium. Off the top of my head, to decrease the KH by 5 degrees (from 7 KH to 2 KH) you would add somewhere around 200 mg/L of NaHSO4 or 40 mg/L Na. Not catastrophic, but worth keeping in mind.

I was experimenting with Sodium Bisulfate because its what i have under the hand, i will use HCL for the experiment. I was just confused why the PH stayed to 6.4 while the KH is at 1.5KH. Like @_Maq_ saidf, it could be that my testing is wrong.

Also I believe you currently target a 1.4 ph drop, whilst life (microbes, fish etc) will continue at a ph of 5, I'm again not sure it's ideal.

I want my PH to be around 7.2 to 7.4 at night.

I may reduce a bit the drop to 1 to 1.2 with a lower kh so i should be more around 6 to 6.2

Right. I'd rather take the higher KH (i.e. higher pH) and feed my plants a little more if I had no other way to lower (control) my KH.

I have tried to increase the amount of fertilizer with no effect at all. (x1.5 EI)


This is an experiment, I'd rather keep to use my plain tap water as it seems to be pretty much perfect in GH ratio except for the KH part

 

[MichaelJ]

@Gorillastomp can you post a full tank shot so we can see what is going on!

As far as the pH measure goes, I think it might be a bit off…. As @_Maq_ suggested - but probably not too far. As long as your pH is at least a bit on the acidic side (below 7) I wouldn’t frazzle too much - Mother Nature is not too picky.

Cheers,
Michael

 

[_Maq_]

I'd rather take the higher KH (i.e. higher pH) and feed my plants a little more

My experience strongly suggests that some species cannot grow in such conditions, even if supported by chelated iron. Admittedly, I don't inject CO2, and never tried chelates stronger than EDTA.

 

[MichaelJ]

My experience strongly suggests that some species cannot grow in such conditions, even if supported by chelated iron. Admittedly, I don't inject CO2, and never tried chelates stronger than EDTA.

True, definitely not a preferable situation and I should have mentioned that plant selection must follow suit. We often recommend plants in the easy category, so hobbyists with less than ideal water can enjoy a planted aquarium.

Cheers,
Michael

 

[John q]

My experience strongly suggests that some species cannot grow in such conditions

Not to play devils advocate here but most species will grow fine in 7 dkh, admittedly some won't. We should be careful about spreading false information. 🙂

 

[_Maq_]

most species will grow fine in 7 dkh

True. It's the phenomenon of recent times that (almost) all hobbyists attempt to emulate tanks they can see on the Internet. These frequently feature more demanding species.
Yet it is perfectly possible to create different, but still beautiful tank in not so favourable water conditions (and without CO2 injection). It's just the species selection is restricted.

 

[Gorillastomp]

@_Maq_ I received my new alkalinity tester.

Tap Water : 135ppm

Bucket Water : 43 ppm

so if we multiply by 0,056 they would be respectively 7,56 dKH to 2,4 dKH

Retested the bucket today and it went up to 6.9 PH. So i guess the Co2 doesn't gas out as quick as i thought. SO i will wait a bit more if it balance out at around 7,4.

@MichaelJ
Current state of the tank is not what its supposed to be, lowered light, co2 due that i have less time to trim. You can refer to my other post for some pictures of what i was experiencing with the plants : Here

Tested TDS between the main tank and bucket, 125 vs 230. So de sodium bisulfate definitely ramp up the tds quite a bit.

Do you think HCL will add less TDS since it will add chloride ?

 

[Oldguy]

plants stunts then create healthy shoot from that stunted tip then stunt again

Thanks for posting water analysis. You do not appear to have any nitrates, or have I missed something. Plants do grow better with a nitrogen feed.

 

[Gorillastomp]

@Oldguy this is the analysis of my tap water.

I do fertilize my tank since i do not have an active substrate. At 1.5x EI levels when i was experiencing these stunting.

 

[MichaelJ]

Do you think HCL will add less TDS since it will add chloride ?

Yes, it will. Off the top of my head it add like1/3rd less to the TDS vs NaHSO4 for the same level of acidity.

Chasing water parameters by the application of extremely volatile chemicals is not advised! Dealing with Hydrochloric acid (HCL), as with other volatile chemicals, is serious business! It will cause severe chemical burns if it get into contact with skin and is highly toxic to inhale. You will have to be in a well ventilated environment and wear protective gear when handling it - such as chemically resistant gloves, eye protection etc. and absolutely no children, pets or unprotected bystanders around when handling it!

Cheers,
Michael

 

[Oldguy]

Do you think HCL will add less TDS since it will add chloride ?

Yes but use dilute, say 0.1Molar HCl and use a dropping pipette. Simple plastic dropping or teat pipettes are very cheap. I use them for adding nutrients, taking the edge off the pH of tap water and adding/removing brake fluid when working on car brakes.
I used to be concerned about TDS but most plants grow better in mineral rich water.
I noted that you used sodium bisulphate because you had some to hand. I sometimes use the potassium equivalent, just a small crystal to a gallon of solution to keep the pH just below 7.

 

[keef321]

@Oldguy this is the analysis of my tap water.

I do fertilize my tank since i do not have an active substrate. At 1.5x EI levels when i was experiencing these stunting.

I have a high PH / KH, I found much more success with plants by adding iron in the chelated form of EDDHA, DTPA and seachem iron. I have best success by dosing the chelated iron when lights come on (as the PH has lowered by the Co2), and dosing on alternative days to any macro dosing, to reduce the chance of precipitation / interaction with phosphates. Might be worthwhile exploring as an alternative, you can find a thread on this issue here Plant deficiencies and the Fe Experiment

 

[MichaelJ]

used to be concerned about TDS but most plants grow better in mineral rich water.

Trying to figure out what you mean by that. Are you suggesting that plants are better off with higher levels of electrical conductivity aka TDS in general? If so, I can’t see how that can be true given that all our plants are from waters with relatively low overall mineral content (low TDS) compared to what we usually offer in our aquariums, not even to delve into what the specific minerals are that makes up the TDS, which is obviously what matters - you don’t want 40 ppm out of say 150 ppm being made up from Sodium - but sulphates, that’s probably fine. For sure, in general TDS is mostly a livestock consideration as it directly impacts osmoregulation, but plants also benefits from lower TDS as well, but to what extent is probably debatable.

Cheers,
Michael

 

[Oldguy]

benefits from lower TDS as well, but to what extent is probably debatable.

If someone has 'liquid rock' out of their tap then I can understand their concerns. However I feel that the hobby has fallen in love with RO water just as people drink bottled water when tap water is fine.
My tap water is moderately soft, I blend it with approx 1/3 rain water and add calcium and magnesium nitrates to the make up water. Then follow EI guidelines.
I used to measure pH and TDS but why bother. I watch the fish & shrimps and plants. I have slightly reduced CO2 injection so that snails have a chance.
Do our aquatic plants come from mineral lean waters, I thought that many are 'weeds' in paddy fields.
Some people on this forum add ammonium compounds to get better growth from their plants and many have nutrient rich substrates. Clearly not following a lean is best policy.
However each to their own.