Strange pH Reading

[shangman]

Hello!

I have a 9 week old 60L aquarium. I am using 100% rainwater in the tank. At first I was planning to add some tap water (10 - 20%) to buffer the water, but my pH readings in the tank have been really strangely high so I haven't. I'm in London, my tap is about 7.8.

The issue is that my pH reading is super high, 1.5 higher than when I put the water in. From 6.6 to 8.2

My rainwater, which I've tested several times over several weeks parameters: 6.5 - 6.6pH, 0 - 0.25Am, 0Ni, 0Na. Alotment water (which I've been using a lot recently) - kH 0, GH 1, Home rainwater - KH 4 GH4 (the butt isn't as big so have to use alotment).

My pH readings over 9 weeks, with kH + GH incase that matters. As you can see, the pH has steadily risen the whole time.

	ph	gh	kh
Rainwater	6.6	4	4
22/06/2020	6.6	4	4
23/06/2020	7
26/06/2020	7.5	4	4
05/07/2020	7.2	5	4
09/07/2020 (this is where I started doing weekly 50% water changes instead of 20%, so a big change here but have still been doing it to no effect from here).	6.8
17/07/2020 (here I added some tap water as I was going to buffer the water with it, but then seeing the high pH I stopped).	7.8	9	7
01/08/2020	7.8	5	5
09/08/2020	7.6	6	4
18/08/2020	8.2	5	5

I can't work out why my pH goes so high in the tank. It seems to be getting worse. I have attached a photo of the tank, it does have some rocks on it, but I checked them all with vinegar before I put them in with no changes. I used XXXX soil, and aquarium sand from my LFS, all washed a lot. I also use TNC complete, I add about 8ml a week (trying to get my frogbit green so adding a bit more than the reccomended dose)

I also read online that rocks shouldn't buffer the water to be so high, and my GH/KH aren't that high which is v confusing. I

I didn't think this is too much of a problem, but 2 cherry shrimp have died in the past 4 days (of about 20), which is why I investigated. I have found moltings around though as well so not sure if it's that this time. have about 20 cherry shrimps and 6 otos in the tank, so I want to make sure I havne't blahblahblahblahed something up for them. I want to keep some bolivian rams or apistos, and I thought they need soft water, so not sure if I can't do that now.


Is this not a problem? Is my test kit blahblahblahblah? Any other ideas? Can pH crash the wrong way?

 

[hypnogogia]

I used XXXX soil,

What is that?
Your lotus is stunning btw.

 

[shangman]

What is that?
Your lotus is stunning btw.

Whoops! Forgot to add it in, it's Moreland Gold Organic Topsoil

Thank you about the lotus, it's such a lovely plant! I'm hoping for a flower at some point


Just had a thought, at the back of the tank II realised 2 weeks ago there was a bit of soil coming over the cap behind the star grass, which I couldn't reach as I had an in-aquarium heater. I just swapped that out for a new heater this weekend outside the tnak, so I could easily add in a big sand/gravel cap. Could that have changed it?

 

[hypnogogia]

I’m not sure, but I suspect that something in the tank is causing your ph to rise.

if you have an open top, it will flower at some point. It’s worth it.

 

[SRP3006]

As you are using compost/topsoil it could have added lime. Lots of compost does hence the need to buy ericaceous compost for plants that need acidic compost.

I checked the link but its doesn't say what's in the compost other than spaghum moss, so the soil could be buffering the pH up, and if I understand correctly when using rain water with very low hardness and ph the buffering effect can be increased, which could have caused the large swing.

After reading more on the website it says the topsoil is blended with natural river sand,could that have had an effect?

 

[shangman]

As you are using compost/topsoil it could have added lime. Lots of compost does hence the need to buy ericaceous compost for plants that need acidic compost.

I checked the link but its doesn't say what's in the compost other than spaghum moss, so the soil could be buffering the pH up, and if I understand correctly when using rain water with very low hardness and ph the buffering effect can be increased, which could have caused the large swing.

If it is my soil (particularly the dodgy bit at the back that's coming up), if I cap it well do you think the effect will go away after a while, or am I screwed? I really don't want to redo the tank with different soil if it's possible!

 

[SRP3006]

If it is my soil (particularly the dodgy bit at the back that's coming up), if I cap it well do you think the effect will go away after a while, or am I screwed? I really don't want to redo the tank with different soil if it's possible!

I'm not an expert in soils or water chemistry so please don't take my advice as gospel

If it is under the sand cap then water will still be circulating through it so although I'm not sure I don't think that would make any difference.

Maybe slowly changing to tap water could minimise the swing and acclimatise your stock to more normal pH levels?

 

[sparkyweasel]

If you have a bit of soil left over, you could put some in a jar with some rainwater and see if it raises the pH. That should tell you if it's the soil or something else.

 

[Melll]

Lovely looking tank

 

[SRP3006]

Is there any reason tap water wouldn't work? Might help minimise the swing.

 

[jaypeecee]

Hi @shangman

I have quickly scanned your thread but you don't appear to mention what you have used to measure pH, KH and GH. This is very important - particularly with rain water.

JPC

 

[shangman]

If you have a bit of soil left over, you could put some in a jar with some rainwater and see if it raises the pH. That should tell you if it's the soil or something else.

Oh this is a good idea, I'll see if we have some left.

Lovely looking tank

thank you!!

Is there any reason tap water wouldn't work? Might help minimise the swing.

It probably would, there were 2 reasons I didn't 1. I really want some SA small cichlids and they're meant to do better in soft water, and 2. I'm the daughter of 2 trained gardeners who are extremely pro rainwater when it comes to delicate plants to help them thrive, so I have a bias towards it. Though I suppose if my pH is this high it makes no difference.

Hi @shangman

I have quickly scanned your thread but you don't appear to mention what you have used to measure pH, KH and GH. This is very important - particularly with rain water.

JPC

Ahh, sorry! I used the API Freshwater Master Test Kit +API GH & KH Test Kit.

 

[zozo]

I'm not an expert in water chemistry..

But the cause of the pH fluctuations could be in the peat soil content... Read the content description closely, in many cases lime is added to peat soils as a buffer to stabilize the pH in the soil. Using such an organic peat soil in an aquarium can affect pH etc. from the water column..

Depending on the age of the substrate it might keep changing and fluctuating. Since the substrate buffers and leaches into the water column. But with doing water changes you actually flushing it out and once it is about done leaching and buffering it will stabilize more to the value of the water you add.

But in an aqaurium pH 8.2 isn't ideal but also isn't problematic... As long as it stays below pH9 it shouldn't be a real problem.

In my case, it's quite standard using tap water only.. The tap water fresh is pH7 but after it's depleted from CO² and the plant metabolism is highest (midday) i have an increase to pH8.5. After lights out, it drops again to around pH 7 at night. This is a normal natural equilibrium.

It's better to deal with what you get as long as it's stable between +/- pH 7 and +/- pH8.5 than trying to control a lower pH with all kinds of additions. Playing too much with pH is mainly the cause of pH to crash.

You also might like to read this about Ph behavior in Peat soils.

The composition of the selected fertilizers also has an influence. For example, ammoniacal nitrogen (NH4+) lowers pH whereas nitrate nitrogen (NO3-) has a pH-increasing effect due to plant uptake. In addition, plants themselves also influence pH by selective uptake of ions.

https://www.eurofins.com/agro/news/unexpected-ph-fluctuations-in-peat-substrates/

 

[shangman]

I'm not an expert in water chemistry..

But the cause of the pH fluctuations could be in the peat soil content... Read the content description closely, in many cases lime is added to peat soils as a buffer to stabilize the pH in the soil. Using such an organic peat soil in an aquarium can affect pH etc. from the water column..

Depending on the age of the substrate it might keep changing and fluctuating. Since the substrate buffers and leaches into the water column. But with doing water changes you actually flushing it out and once it is about done leaching and buffering it will stabilize more to the value of the water you add.

But in an aqaurium pH 8.2 isn't ideal but also isn't problematic... As long as it stays below pH9 it shouldn't be a real problem.

In my case, it's quite standard using tap water only.. The tap water fresh is pH7 but after it's depleted from CO² and the plant metabolism is highest (midday) i have an increase to pH8.5. After lights out, it drops again to around pH 7 at night. This is a normal natural equilibrium.

It's better to deal with what you get as long as it's stable between +/- pH 7 and +/- pH8.5 than trying to control a lower pH with all kinds of additions. Playing too much with pH is mainly the cause of pH to crash.

You also might like to read this about Ph behavior in Peat soils.

https://www.eurofins.com/agro/news/unexpected-ph-fluctuations-in-peat-substrates/

Thank you for the response, it's very informative! I'm glad that it will eventually stop/become less drastic, I think I'll just keep doing what I do and wait for the equillibrium (and use a soil that definitely doesn't have lime next time, and less peat!). I'm going to add more sand cap where the soil is exposed this weekend, I was thinking that perhaps where it's exposed it's leaching more into the water column. If it could leach a bit less that'd not be so bad, and more consistant over time.

I definitely don't want to faff around with pH changing chemicals, it sounds like a losing battle, thank you for the advice and explainations.

 

[zozo]

(and use a soil that definitely doesn't have lime next time, and less peat!)

I guess the lime is exclusively added in peat soils aimed to use for horticulture. But there are organic peat soils available for aquatic use in pond shops that do not contain any lime. And they can perfectly be used in an aquarium.

I have a small tank in my garden, did set it up about 3 years ago and it contains Velda Lelite pond soil for lilies it is based on peat and blue clay... And it works a charm, it grows plants like a champion.
https://www.ukaps.org/forum/threads/mission-bathtub-and-the-pollywog-party.60722/post-611163

I specifically choose the bleu clay variety because it holds a better consistency submerged than the regular peat-based pond soils without it.

 

[shangman]

I guess the lime is exclusively added in peat soils aimed to use for horticulture. But there are organic peat soils available for aquatic use in pond shops that do not contain any lime. And they can perfectly be used in an aquarium.

I have a small tank in my garden, did set it up about 3 years ago and it contains Velda Lelite pond soil for lilies it is based on peat and blue clay... And it works a charm, it grows plants like a champion.
https://www.ukaps.org/forum/threads/mission-bathtub-and-the-pollywog-party.60722/post-611163

I specifically choose the bleu clay variety because it holds a better consistency submerged than the regular peat-based pond soils without it.

Ahh you made that lovely bathtub! I really love that journal

Thank you for the soil rec, I'll use it for my next tank (which incidentally will be this weekend as my tank + a lovely nano planted tank at my LFS has seduced my dad into getting one that we're working on together! Hooray, MTS is setting in!!)

 

[zozo]

Thank you too...

Would love to read the journal from you oncoming project... And see the results...

 

[shangman]

Thank you too...

Would love to read the journal from you oncoming project... And see the results...

You will! I set up my last tank before finding this site, very excited to share the next one I've read all the featured journals and they're so inspiring and exciting, and I love the bredth of styles and ideas people have., can't wait to start to contribute myself