Sudden PH drop (1 Viewer)

[adahm]

So today, by accident, I noticed a PH drop within two hours of adding top off water. I was not checking for it. I had my PH probe in the DT and was measuring 8.23 prior to adding the water. I just forgot turn off the PH monitor.

At 7:30 pm I turned on the lights checked the PH and it was 8.23. We were out today so this 3hrs later than usual.

Noticed return level was low, so I proceeded to add about 1 gal of RO/DI.

At 9:30 pm I came by and noticed PH at 7.27. I had just opened the windows as there was some in the house from cooking.

Just checked at 11:30 pm and PH is up to 7.76.

Not sure what is going on here. Should I be adjusting PH of top off water before adding? Does the PH change this much when topping off. Tank is 90 gal, sump is 20gal with 2/3 full. About 120 lbs of love rock to give an idea of water volume. Top off water was made last Friday. this was the last of it in a 5 gal bucket.

 

[Diesel]

How old is your PH probe? Do you dose and what? When is it the last time you calibrate your PH probe?
And one more thing, I do like to have a reef tank one day with "LOVE ROCK", LOL!

 

[adahm]

Lol!!!

Not sure about age of probe/meter, bought it second hand.

As far as calibration I trusted the last owner when he said it was calibrated. Don't have reference fluids to calibrate against.

 

[Diesel]

If I was you I should not panic on the tank but check your probe tomorrow or over the weekend. A new probe cost about $40 calibrate fluids for the high 7 and 10 about $5.
If this was a used probe my two cents are replace it.

 

[tektite]

It may partly be from lights out ph drop. Take measurements every couple hours tomorrow to see if you get the same drop at the same time.

 

[inigomontoya]

I have been through this drama a couple of times. The first was a bad probe, the second was fixed with a recalibration. Keep a cheap ph kit around (your old API or something) and doublecheck your results. I had a similar full point drop within a couple of hours and checked with a kit and it read the normal 8.3 range. That time was the probe- next time recalibration fixed it and I didn't panic as much. For that big a drop, that fast, unless a kid dropped a bottle of vinegar in the tank, it is very likely the probe.
City pets sells calibration fluid for a couple of bucks a packet.
Regardless you want to calibrate and lightly clean (with a soft rag or new, extremely soft toothbrush) the probe every couple of months.

 

[adahm]

Thanks for the info. I have to get a Ca and PO4 test kits anyway the redsea one got from petco still reads ammonia and nitrite in my tank (never changed levels nh3, no2, and no3 in 4 months) so I don't trust any one of the other tests in the kit. Plus I find it very hard to match colors.

Any recommendations for tests in which colors are easily discernible?

 

[Midwinter]

Do you have enough surface water movement? It might be the problem; mine was the same now my PH stay at 7.9 for months now. Hope it help