Day four of in-tank curing

[AllSignsPointToFish]

I'm on day 4 of in-tank curing of the live rock. Everything is looking okay except for kH. Here is the rundown:

Temperature - 79-80°F
SG - 1.025-1.026
pH - 8.0 (a little low)
Ca - 410-420 ppm
NH3 - 0.5-1.0 ppm
NO2 - 1-2 ppm
NO3 - 20-40 ppm (high but expected due to curing cycle)
PO4 - 0.25-1 ppm
KH - >12 dKH

I assume the pH is a little low just due to the curing cycle. I only have two days worth of data, but ammonia and nitrite and trending downward, and nitrates are trending upward, so all of that should indicate a normal increase in nitrogen-fixing bacteria.

I haven't been adding and bicarbonate/carbonate buffer. I don't know why the KH is so high. Any ideas why KH is so off?

 

[Randy Holmes-Farley Verified Community Expert]

Let's see what it actually is by adding a second syringe of titrant fluid and getting to the endpoint. Then add the values together.

Some salt mixes start above 12 dKH. What mix are you using?

Any cement or artificial rock in the system?

FWIW, some of the organic matter present in curing rock can get swept up in a measure of alkalinity, so the number may read false high for that reason.

 

[AllSignsPointToFish]

Okay, thanks Randy. I'll do that.

I'm just using plain old Instant Ocean, nothing fancy.

All rocks and sand are supposed to be natural. No cementitious material has been added in any form.

I didn't realize organic matter could affect the alkalinity measure. I thought maybe the silt from the live sand, being finely divided calcium carbonate, could've been elevating the alkalinity. However, the tank has been clear for three days, so the amount of calcium carbonate suspended in the water is minimal.

 

[Drauka99]

IO Reef Crystals reads 11-12 for me.

 

[Randy Holmes-Farley Verified Community Expert]

I didn't realize organic matter could affect the alkalinity measure. I thought maybe the silt from the live sand, being finely divided calcium carbonate, could've been elevating the alkalinity. However, the tank has been clear for three days, so the amount of calcium carbonate suspended in the water is minimal.

It certainly would give a false high reading if there is any suspended in the water that was tested.

 

[AllSignsPointToFish]

I didn't have to do the double volume test. The dKH was 11 tonight. Still a little high, but at least believable and in-range.

Ammonia was zero for the first time, and nitrites continue to trend downward.

 

[Randy Holmes-Farley Verified Community Expert]

OK, so I wouldn't worry about it.

Happy Reefing.