HI774 vs H736 reagents

normal · Feb 8, 2021

Hi ,

I have bought the HI 774 phosphate ULR checker from Hanna, and I'm very satisfied with the tester as it makes me actually not hate testing phosphates, but I'm having an issue sourcing the 774 reagent in my area. All LFSs here seem to carry the 736 reagent packs, and the 774 is always with backlog in delivery.

Wanted to ask if anyone knows if they are interchangeable. If so, I would buy 736 and use on 774.

I'm asking this, because I think there might be the possibility of them being the same tester, only with different math functions to show phosphate ppm or phosphorous ppb.

Cheers!

Shirak · Feb 8, 2021

I have used the ulr phosphorus tester reagent with my ulr phosphate tester and it seemed to work just fine. I ran back to back tests with each and the ulr phosphate tester gave me the same reading with both reagents

lafarrow · Feb 8, 2021

Shirak said:
I have used the ulr phosphorus tester reagent with my ulr phosphate tester and it seemed to work just fine. I ran back to back tests with each and the ulr phosphate tester gave me the same reading with both reagents

That is great to know. Kinda surprised but glad to know

normal · Feb 9, 2021

Shirak said:
I have used the ulr phosphorus tester reagent with my ulr phosphate tester and it seemed to work just fine. I ran back to back tests with each and the ulr phosphate tester gave me the same reading with both reagents

That's great news. Thanks!

MNscoe · Jul 17, 2025

I have the reverse problem, a HI736 ULR Phosphorus tester with HI774 ULR Phosphate reagent packets. I did a back to back test and both reagents gave me a "zero" phosphate reading (which is good consistency, but as a newbie I'm trying to figure out if zero phosphates is OK/normal or not).

Shirak · Jul 17, 2025

0 phosphate is not good IMO. I like to be between .05ppm to .1ppm You need some for the corals to metabolize. If it was very pale or unchanged and no hint of blue after the 2min shake and 3min timer then it is reading correct and there isn't any phosphate in the water. The test is the same it's just a difference in how the Hanna reports the results.