Ph reads differently at different tank levels

[bellatrixferox]

I have a strange phenomenon happening here. Doesn't seem to be affecting much, but I'm wondering if anyone has any thoughts on it.

This is long, so I apologize in advance.

I tested my water this AM before doing my water change because my Jack Dempsey looked a little washed out. The Ph was unusually high (8.8 approx). Normally it's around 8. Ammonia/nitrate/nitrite was 0/0/0 as usual. I proceeded with my water change, and on a whim I tested the tank water again at 50% empty. And got the normal reading of 8. Not really sure how that's even possible. I tested the water coming out of the faucet, and got 8. My first assumption would be that the faucet water was higher than usual during my last water change (another 50% 2 days ago, I'll get to that in a minute). But....the difference at the lower level doesn't really make sense. The readings were done with a Master Test kit, so I'm reasonably sure they're accurate.

The tank is a 56gal column (so, tall and narrow). There are 4pcs driftwood, an aerator, several live plants-- all of which allegedly keep the Ph down. There is one JD in the tank, and 1 king tiger pleco.

The reason for my water changes is because I treated the tank with victoria green this past week. I thought my JD might have some sort of external parasite, because she's got a red spot on her head and missing scales. The more I look at it, the more I think she just scratched herself on a rock or something (eyeroll). She's very assertive and active, never hides. She also showed exactly zero signs of being sick otherwise. Very active, great color, excellent appetite, no clamped fins, etc. The washed out color this morning may have been an overreaction by me, actually, I had just turned the lights on. I don't think the treatment was a factor in changing the Ph. Reason being, a couple of weeks ago I did a water test before my change and also got a high reading at the top also. I did not test the water again at the halfway mark that time. And.....1 week or so after the high reading, I did the same thing (tested the water prior to the water change) and got my regular Ph.

My fish seem pretty fine. And as I'm typing this my JD's color is coming back lol. She already ate voraciously this morning as well. The different levels at the different levels is just very weird to me.

 

[aseradyn]

Maybe look at your circulation and where your heater is?

This is a long shot, but water with different levels of dissolved solids can have slightly different densities, and stratify. Temperature will do that, too, because warm water is less dense. When you get water with a thermocline or other 'cline, it may need mechanical mixing to spread out the chemistry.

I've set up a halocline in as little as 6" of water. Pretty cool to see it when you add dyes.

Or, it could be completely something else! This is just what popped into my head when you mentioned a deep tank.

 

[Mcfly]

IF you're using something similar to an API Master test kit, make sure you wait a few minutes before reading... The reading changes over time (I wait 5 minutes) so that might explain the inconsistency, the other factor in pH is water hardness (as mentioned above aka dissolved solids) so next time this happens, check the gH, and see if there's a correlation.

 

[Ingy]

1. pH needs to be read right away. The reading will change very quickly.
2. pH changes throughout the day and night. Different times can mean different reading.
3. Saying an API "master" test kit must be accurate is like saying a top model Geo Metro must be fast because it's the top model. API is the bottom end of test kits, but fortunately generally good enough for freshwater. I will use their nitrogen tests but not the pH test. For saltwater tanks they are only good enough for throwing at your frisbee that got stuck in a tree.