Phosphorus Ultra Low Range Colorimeter HI736 Hanna Checker - Marine Water

Click on image to zoom
View full size image

More Views

  • BRStv Investigates: Which is better, Hanna Phosphate or Phosphorus Checker?

Phosphorus Ultra Low Range Colorimeter HI736 Hanna Checker - Marine Water

78% Recommend this to a friend (14 of 18)

SKU: 208630
Please wait...


1-3 day service on orders over $249

What's this?

You could earn
245 points
($2.45 off a future purchase!)
Ships Monday

Quick Overview

Monitoring phosphorus concentration in saltwater is important because it can cause corrosion if levels are too high. The Hanna HI736 Checker HC Handheld Colorimeter for Phosphorus ULR bridges the gap between simple chemical test kits and professional instrumentation. Accurate, affordable and easy to use. First, zero the instrument with your water sample. Next, add the reagents. Last, place the vial into the Hanna Phosphorus Checker, press the button and read the results. Done.

Ask a question

Product Questions

Which checker should I use for a reeftank the hi713 or hi736 to check for phosphate?
Question by: John on May 28, 2016 11:19:00 AM
Great question!
We use the Hi713 in most cases as it is easier to use and read over the phosphorus which requires additional calculation to convert to phosphate.
Answer by: Connor (Admin) on Jun 3, 2016 1:35:00 PM

Full Details

Hanna Checker Phosphorus Ultra Low Range Manufacturer's Manual

Hanna Checker Phosphorus Ultra Low Range Manufacturer's Literature


  • Easier to use and more accurate than chemical test kits
  • Large, easy to read digits Auto shut-off
  • Dedicated to a single parameter
  • Designed to work with HANNA's reagents
  • Uses 10 mL glass cuvettes
  • Small Size, Big Convenience
  • Fits in the palm of your hand


  • Range: 0 to 200 ppb
  • Resolution: 1 ppb
  • Accuracy: ±5 ppb ±5% of reading
  • Light Source: LED @ 525 nm
  • Light Detector: Silicon photocell
  • Environment: 0 to 50°C (32 to 122°F); RH max 95% non-condensing
  • Battery Type: (1) 1.5V AAA
  • Auto-off: After 2 minutes of non-use and 10 seconds after reading
  • Dimensions: 81.5 x 61 x 37.5 mm (3.2 x 2.4 x 1.5")
  • Weight: 64 g (2.25 oz.)
  • Method: Adaptation of Standard Method for Examination of Water and Wastewater, 20th edition, Ascorbic Acid method



Items 1 to 12 of 18 total

  1. 1
  2. /
  3. 2
  • Test-retest reliability frustrating, but really the kit to have By jmfugett on 5/7/2017

    I use Hanna ULR and Red Sea PO4 kits. I use them both at times to verify results. The Hanna is very satisfying as it gives you a very refined number. The only problem is if you test 3 (4,5,6 or whatever) times you will get as many different results. Sometimes the swings are pretty severe. I have had results that run from 3 to 22 between two tests. If you can get past the fact that this colorimeter is trying to discriminate between very tiny amounts of phosphorus you won't feel as crazy about the swings. I have been using the Hanna ULR for over a year and as my PO4 levels decreased to at or near 0 and my experience and routine for taking tests have improved, the swings are not as bad and less of an issue. If testing for PO4 is important to you, you really need to get this colorimeter.
  • Best Option, But Nowhere Near Perfect By Patrick on 5/5/2017

    Seems to work okay. My main problem is with the device itself and the manufacturer's instructions.

    First, after you zero the meter, you have to add the powder to the vial and shake gently for two minutes. But, the meter shuts off after 3 minutes of inactivity. If you don't prep the powder and get it all ready to pour before zeroing, your meter will turn off before the two minutes of shake time is up. Then, since you use the same vial to zero and read, you have to start over, and you've wasted the test reagent. Seriously Hanna? You say the unit will test at least five thousand times before needing a new battery. If you test phosphates EVERY SINGLE DAY, this means the battery will last over thirteen years. If you test once a week, the battery will last 96 years. Once a month? You'll be able to use a single battery for 416 years. Now quite obviously, that's ridiculous.. batteries lose their charge naturally over time, so the battery in your checker is likely to die of natural causes before you wear it out via testing. So that begs the question, why is it so important to shut the meter off after 3 minutes of inactivity DURING YOUR TESTING PROCEDURE?! Why not bump it up to 5 minutes? Or even 10? Give me a worse case scenario... battery usage doubles and you only get 2,500 readings out of a battery? The battery will still die naturally before you wear it out with testing.

    Second, the instructions are terrible. If you're going to give us only a minute of breathing room during the testing procedure, why not tell us this so we can prepare the reagent beforehand? If you watch Youtube videos or read forum posts about this checker, you'll learn this pretty quickly. But why not put it in the instructions? This leads me to question all the other directions as well. You say "shake gently" for two minutes. Well, how vigorously is "gently?" I still have some undissolved powder shaking around in the vial after two minutes. Is this normal? Am I not shaking hard enough?

    $50 is a lot to spend on a test kit. I don't mind if the procedure is complicated, just tell me how to use the device properly. I don't want to pay $50 to have to figure things out on my own.
  • Phosphorus Hanna checker By Rafaylin on 5/3/2017

    Awesome phosphorus Hanna checker works really good highly recommended for the ultra-low phosphate..
  • Best Option Out There By Forsaken77 on 2/26/2017

    Unfortunately this is the best option out there for measuring low range phosphates. For those that don't know, you take the sample reading, multiply by 3.066, then divide by 1,000. This will give you phosphates in ppm. The reason you always get slightly different readings is because it's reading in ppb, which is a VERY low range to begin with and the meter has a +/- percent of accuracy because of the ultra low range.

    The problem, like others have stated, is getting ALL of the reagent into the vile even if you do it perfectly. You have to flick it all in one corner of the packet and some gets stuck in the corner. So by tapping on the packet to get it in the very tiny vile, you end up spilling a bit.

    Then, it says to shake for 2 minutes before putting the vile back in for the reading, but according to the instructions, the meter automatically shuts off after 2 minutes. Figure that one out. I haven't tested if it gives you the time to shake for 2 minutes and then will shut off 2 minutes after that, but I usually shake for 1 minute 50 seconds so I have time to wipe the vial clean and get it in the colorometer quick enough to hold the button down for its 3 minute countdown to let things settle.

    I wish there was a simple monitor with a probe that just constantly measured phosphates and nitrates. It seems these are the only 2 parameters that can't be monitored,yet they are some of the most important factors in determining algae issues.

  • Hanna H1736 By Bori on 1/22/2017

    Great and simple! Nothing more to be said about this item!
  • Great product By Paul on 10/2/2016

    This has been a great device for determining phosphate levels in a reef tank. Easy to use once you get used to the procedure. Number readout and no guessing colors.
  • It really is easy By Aaron on 7/18/2016

    I was hesitant to grab this because of a few reviews that stated it was difficult to get all of the reagent in the curvet but if you flick the packet a couple of times to get the reagent down to the bottom corner, cut the packet like instructed, and fold/roll one side to create a half funnel, it just couldn't be any easier.
  • Good By Niko on 4/3/2016

    I like it!
  • Awesome By crocogator106 on 3/30/2016

    Great piece of equipment. Exact digital readout-no trying to match colors and guessing. Very easy to use.
  • Hanna check ultra low By Nate on 3/20/2016

    Getting accurate readings and working great. you need to make sure your glass vials are cleaned and use all the reagent. Then it will work like a charm.
  • Get The Phophous Test By Sunghoon on 3/14/2016

    This one still doesn't read low enough. I should have bought the phosphorus test and done the conversion. Algae is still causing levels to be to low.
  • decent product deficient marketing approach By MaLi on 2/20/2016

    Seems to work well, but I was amazed by the fact that with the meter there are only eight (8) reagent tests. Strange and cheap given that a pack of 25 is only $9. In my opinion really bad marketing strategy. A bit of a ripoff. I will not recommend to others though I believe is a decent quality product. Hopefully marketing will learn something.