AN ACCURATE AND PRECISE METHOD FOR MEASURING IODINE

[Randy Holmes-Farley]

Some recent results show Iodine well above target levels in a couple of salt mixes (which is fine - it depletes)
I.O. and Reef Crystals checked in at 0.20ppm Iodine here.
https://www.reef2reef.com/threads/the-ultimate-salt-test.949805/post-10794608

(Also my I.O. made fresh is above 0.10 ppm Iodine too, so the results in the thread are consistent with what I've seen as well.)

Did you ever see a bump up just from a water change, and were there many water changes during this depletion curve?

What you feed (and, of course, what's in the tank, especially certain types of algae) may also make a big impact on the final steady state in the absence of dosing.

 

[Rick Mathew]

Some recent results show Iodine well above target levels in a couple of salt mixes (which is fine - it depletes)
I.O. and Reef Crystals checked in at 0.20ppm Iodine here.
https://www.reef2reef.com/threads/the-ultimate-salt-test.949805/post-10794608

(Also my I.O. made fresh is above 0.10 ppm Iodine too, so the results in the thread are consistent with what I've seen as well.)

Did you ever see a bump up just from a water change, and were there many water changes during this depletion curve?

So two things....I do a continuous water change...about 30%/Month ( 1.5gal/day) so I don't have occasion to see any big shifts due to water change. The water change amount was consistent over the testing period (30 days)...Second I use Red Sea Blue Bucket and for a while I tested every new bucket and found they were very consistent on their Iodine Level .....05 to .07 ppm....mostly at the upper end. So for sure the rate of depletion would be affected by the continuous water replacement.

 

[taricha]

And so now you get a good look at the depletion rate of the 0.06ppm Iodine in my tank.

One last demonstration of this method and Iodine trends in my tank. Here's showing the detected iodine input from water changes with a bag of Reef Crystals.
I did two 3 gallon changes in my 65 gallon system. So two x 4.5% water changes. The inputs are obvious and easily measured.

(this level of increase - 0.020 from 9% change implies Iodine of ~0.2ppm in the bag of reef crystals - which is in line with the collection of ICP results mentioned earlier.)

I.O. and Reef Crystals checked in at 0.20ppm Iodine here.
https://www.reef2reef.com/threads/the-ultimate-salt-test.949805/post-10794608

 

[Dennis Cartier]

Because the HI707 is not common in the reef stores, I started looking to see what else I have that uses a 525nm LED. I have a HI736 (ULR Phosphorous) and HI782 (Nitrate High Range). My question is does the compressed scale that other testers report in, compared to the HI707's 0-600 ppm, affect the resolution of the test substantially?

Update: It looks like I figured out the answer. The resolution of the HI782, 0 - 75.0, resolution of 0.1 ppm, accuracy +/- 2.0 ppm, +/- 5% of reading, compares well to the HI707, 0 - 600 ppb, resolution 1 ppb, accuracy +/- 20 ppb, +/- 5% of reading.

I just needed to shift the decimal place.

 

[Dan_P]

Because the HI707 is not common in the reef stores, I started looking to see what else I have that uses a 525nm LED. I have a HI736 (ULR Phosphorous) and HI782 (Nitrate High Range). My question is does the compressed scale that other testers report in, compared to the HI707's 0-600 ppm, affect the resolution of the test substantially?

Update: It looks like I figured out the answer. The resolution of the HI782, 0 - 75.0, resolution of 0.1 ppm, accuracy +/- 2.0 ppm, +/- 5% of reading, compares well to the HI707, 0 - 600 ppb, resolution 1 ppm, accuracy +/- 20 ppb, +/- 5% of reading.

I just needed to shift the decimal place.

I obtainec good results using the LR Phosphate Checker.

 

[Dennis Cartier]

A big thanks to @Rick Mathew , @taricha and @Dan_P for working this out. It is very helpful for monitoring iodine levels, especially when setting up daily dosing.

I found that iodine appears to accumulate and easily become elevated once I addressed the depressed level of iodine. Uptake of iodine appears to slow down dramatically once the historical deficit is addressed.

This test method has been invaluable for tweaking my daily iodine dosing.

 

[Rick Mathew]

A big thanks to @Rick Mathew , @taricha and @Dan_P for working this out. It is very helpful for monitoring iodine levels, especially when setting up daily dosing.

I found that iodine appears to accumulate and easily become elevated once I addressed the depressed level of iodine. Uptake of iodine appears to slow down dramatically once the historical deficit is addressed.

This test method has been invaluable for tweaking my daily iodine dosing.

You are most welcome...Really glad to see it is helpful to others in the community.

 

[taricha]

I found that iodine appears to accumulate and easily become elevated once I addressed the depressed level of iodine. Uptake of iodine appears to slow down dramatically once the historical deficit is addressed.

I can't say for sure if that's what's going on, but it does fit with observations. People who don't intentionally add iodine usually are depleted, and people who do add iodine according to a schedule without testing often find that their iodine is well higher than their intended target value.

 

[Rick Mathew]

I can't say for sure if that's what's going on, but it does fit with observations. People who don't intentionally add iodine usually are depleted, and people who do add iodine according to a schedule without testing often find that their iodine is well higher than their intended target value.

I agree that's been my experience...For me that was one of the motivators to have a more accurate test.