Crazy high pH after water changes

Darsh · Sep 22, 2019

Hi everyone, I'll try to keep this short.
For the past few months I've been trying to kure my homemade rock.
I started in buckets, then when the pH had dropped below 10 I put them all in my empty 100L tank thinking the extra volume would speed things up.

Anyway, they didn't so my rocks are back in buckets.
I did a 100% water change on my tank and the next day my pH was back up to 10!

I took out all the sand which is dolomite and did a 100% water change yesterday and now the pH is back up to 9.5! Probably it will keep rising like before.

What is happening???

I'm doing everything with tap water and it's pH is about 7.5

There nothing in the system apart from glass, plastic and silicone. What could be doing this??

ShadowReef · Sep 22, 2019

Darsh said:
Hi everyone, I'll try to keep this short.
For the past few months I've been trying to kure my homemade rock.
I started in buckets, then when the pH had dropped below 10 I put them all in my empty 100L tank thinking the extra volume would speed things up.

Anyway, they didn't so my rocks are back in buckets.
I did a 100% water change on my tank and the next day my pH was back up to 10!

I took out all the sand which is dolomite and did a 100% water change yesterday and now the pH is back up to 9.5! Probably it will keep rising like before.

What is happening???

I'm doing everything with tap water and it's pH is about 7.5

There nothing in the system apart from glass, plastic and silicone. What could be doing this??

Hmmm, interesting puzzle! Keen to see what others say on the matter. You say homemade rock...what is the rock made from? Are you sure it's not the rock itself causing the pH issues? The other thing I would consider is the test itself..have you tried testing with a different test kit to confirm the results? Some test kits go bad even before their end date and sometimes human error plays a part (I'm sure you're not doing it incorrectly so no offense meant, but I do daily tests for all kinds of things and every now and then I get an odd result and realise I should have re-read instructions before trying from memory lol)

Vinman · Sep 22, 2019

Homemade rock???? Please elaborate

Darsh · Sep 22, 2019

ShadowReef said:
Hmmm, interesting puzzle! Keen to see what others say on the matter. You say homemade rock...what is the rock made from? Are you sure it's not the rock itself causing the pH issues? The other thing I would consider is the test itself..have you tried testing with a different test kit to confirm the results? Some test kits go bad even before their end date and sometimes human error plays a part (I'm sure you're not doing it incorrectly so no offense meant, but I do daily tests for all kinds of things and every now and then I get an odd result and realise I should have re-read instructions before trying from memory lol)

No problem, that's why I posted here because clearly I'm doing something wrong

I'm using a pH meter. It's a cheap one and I don't have any calibration powder but at the moment I don't think it's important as my tap water shows 7.5, my buckets with rock show 9, my bucket with sand shows 8.1 and my tank shows 9.5 consistently. They might not be the most precise readings but I've tested and retested and they come out the same. So there must be something buffering the water.

Vinman said:
Homemade rock???? Please elaborate

I made the rock based on this thread:

DIY Rock Tutorial/Info Thread (Rocks, walls, floors, etc.)

Joining a new forum is kinda like starting fresh for me, and I definitely love to contribute when I can. I've casually scanned the threads in this area and haven't seen much in the way of DIY rocks and rock projects. Since making DIY rock is my business, I'd like to think of myself as somewhat...

www.reef2reef.com

just white cement, perlite and sand. But that's all out of the tank now anyway.

motortrendz · Sep 22, 2019

Cement takes time to cure. Just like when you make cement frag plugs you need to soak them for a while in water to cure them. Rinsing multiple times.

Vinman · Sep 22, 2019

Let's start from your water source what's the pH have your water before you send it through your r o d i system is it the same some city water has a pH has highest 10 or 11

ShadowReef · Sep 22, 2019

I think it's the cement causing the issue. A quick google has told me some cements have a pH of 13! Some also have binding agents that have a pH of 11. Only thing I can suggest is look at the brand and see if there is any info online to confirm

Darsh · Sep 22, 2019

motortrendz said:
Cement takes time to cure. Just like when you make cement frag plugs you need to soak them for a while in water to cure them. Rinsing multiple times.

I mentioned in both my previous posts that the rocks are in buckets and not in my tank.

The buckets with rocks reads 9.

I did a 100% water change yesterday into an empty tank with water at a pH of 7.5 and now one day later it reads 9.5.

Again it's an empty tank, this water never made contact with the rock.

Vinman · Sep 22, 2019

ShadowReef said:
I think it's the cement causing the issue. A quick google has told me some cements have a pH of 13! Some also have binding agents that have a pH of 11. Only thing I can suggest is look at the brand and see if there is any info online to confirm

He said rock wasn't in tank any more I think

Darsh · Sep 22, 2019

Vinman said:
Let's start from your water source what's the pH have your water before you send it through your r o d i system is it the same some city water has a pH has highest 10 or 11

Tap water, pH 7.5

Darsh · Sep 22, 2019

ShadowReef said:
I think it's the cement causing the issue. A quick google has told me some cements have a pH of 13! Some also have binding agents that have a pH of 11. Only thing I can suggest is look at the brand and see if there is any info online to confirm

A few months ago it read 16! But to be honest that has nothing to do with my question haha.
These rocks have been kuring for 3-4 months in buckets.
Only recently I added them to my tank, again with tap water.
Then i took them out and have done 2 100% water changes and something in the empty tank is still buffering my water.

ShadowReef · Sep 22, 2019

Vinman said:
He said rock wasn't in tank any more I think

Oh sorry, missed that part

ShadowReef · Sep 22, 2019

Short of the test being wrong, I'm out of ideas. Doesnt make sense to me that an empty tank with nothing but salt water can increase pH to this level. An acidic reading would make more sense because it would likely be an oxygen issue. Tap water ranges from a pH of 6 to 8.5 so if your test is 1.5 out then your tap water would be 6.0 and your tank would be 8 if you're saying its 9.5 now.

andyg1960 · Sep 22, 2019

Are you sure your testing is accurate?

Darsh · Sep 22, 2019

ShadowReef said:
Short of the test being wrong, I'm out of ideas. Doesnt make sense to me that an empty tank with nothing but salt water can increase pH to this level. An acidic reading would make more sense because it would likely be an oxygen issue. Tap water ranges from a pH of 6 to 8.5 so if your test is 1.5 out then your tap water would be 6.0 and your tank would be 8 if you're saying its 9.5 now.

I agree, that's why I'm stumped. Also, it's not saltwater, it's regular tap water.

andyg1960 said:
Are you sure your testing is accurate?

No I'm not sure, I'll buy some Salifert pH sometime in the next few days, I'm just sure that there's a 2 level increase in one day for no reason.

andyg1960 · Sep 22, 2019

If you have an LFS nearby, bring them some water to verify testing.

Randy Holmes-Farley · Sep 22, 2019

Darsh said:
No problem, that's why I posted here because clearly I'm doing something wrong
I'm using a pH meter. It's a cheap one and I don't have any calibration powder but at the moment I don't think it's important as my tap water shows 7.5,

That's not at all a reasonable expectation. Uncalibrated pH meters are worse than useless.

Darsh · Sep 22, 2019

Randy Holmes-Farley said:
That's not at all a reasonable expectation. Uncalibrated pH meters are worse than useless.

Yes I'm sure that it's not accurate but if my tap water reads "x" then my empty tank water reads "x plus 2", then something must be buffering the water no?

Randy Holmes-Farley · Sep 22, 2019

Darsh said:
Yes I'm sure that it's not accurate but if my tap water reads "x" then my empty tank water reads "x plus 2", then something must be buffering the water no?

No. It doesn’t work that way at all.