New KH Monitor - Alkalinity Readings

[ihavecrabs]

So I just set up my new KHG Monitor and ran a few tests. Everything tested near perfect from the initial test run. Here are my readings from all my test kits.

What do you guys think is more accurate?

Hanna Test 1 (Reagent near end) - 8.1
Hanna Test 2 (Reagent near end) - 8.1
Hanna Test 3 (New Reagent) - 7.8
Hanna Test 4 (New Reagent) - 7.8
Salifert Test 1 - 7.5
Salifert Test 1 - 7.5

KH Guardian Tests:

11/11 09:57:13 W.113 %0 KH :8.14
11/11 10:11:35 W.111 %0 KH :8.18​

I set my KH Guardian to correct its readings by -0.53 based on taking the mid point of Hanna tests 3/4 and Salifert test 1/2 and averaging them.

I'll be sending a icp test out in the next month or so and that may help validate.

What is everyones thoughts?

 

[ca1ore]

A KH accuracy spread of 0.68 seems immaterial to me. I’d be much more interested to know how precise the guardian is. So if it’s ‘off’ by x.x; it’s always off by that amount.

 

[LobsterOfJustice]

I have my KHG adjusted based on the Salifert kit results. Remember to readjust when you make up a new batch of reagent

 

[ihavecrabs]

Agreed, I'm less worried about which one is correct and keeping things stable.. But if I can get it stable and correct, why not!

 

[ihavecrabs]

@ca1ore @LobsterOfJustice

Since you both have experience with this system, how are you replacing the saltwater used for the tests?

Luckily, my system is large enough (200g) that it would likely take a while to drop 0.001 s.g. to 1.025 (I would think), but I am also doing a non-water change system with ATI essentials.

My thoughts are, I could

1. add saltwater in the same ratio it is taken (~65ml a test)
2. increase salinity slightly in my ATO container (Not sure how the PUMP would handle it?)
3. Add saltwater sporadically when confirming salinity drops.

Interested to see what you are doing..

 

[ihavecrabs]

I think I answered my own question with some math.. Let's see if it checks out.

System size (water volume only) 200 g = 757 L or 757000 ml
~65ml a test, 12 tests a day (one every two hours) = 780ml/day or 5460ml/week

So weekly, the salinity change would be (757000ml - 780ml) / 757000ml = 0.00103% change

35ppt (1.0264) * 0.00103 = 35.964ppt or 1.0263 which is a change of -0.0001 s.g. a week or 0.036 ppt weekly

If I went with the test every 240 minutes rather than every 120 minute then it would be -0.00005 s.g. a week or 0.018 ppt weekly.

So, in order for it to fall to 1.025 (33.188) at a test every 2 hours, it would take ~50 days assuming no re-tests or manual tests initiated.

 

[ca1ore]

Sorry if I was unclear. I am not using the KH guardian, I was just curious how precise it is (as opposed to accurate).

 

[LobsterOfJustice]

The waste water from the test can be directed back to the tank. The reagent is just acid so at the end of the test it’s just a small volume of very low alkalinity water that is being returned to the tank.

 

[ihavecrabs]

The waste water from the test can be directed back to the tank. The reagent is just acid so at the end of the test it’s just a small volume of very low alkalinity water that is being returned to the tank.

Yeah, I read that. I take it that is what most people do.

 

[ihavecrabs]

Sorry if I was unclear. I am not using the KH guardian, I was just curious how precise it is (as opposed to accurate).

My experience so far says it is very precise, but I do not know on the accuracy as I am comparing it to other hobby grade test kits.

It is hitting the same result over and over again and seems to be following a slight diurnal pattern. I just turned it to every two hours today so I'm looking forward to seeing the full 24 hours.

Time will tell. Here are the last three tests:

11/11 13:50:12 W.122 %0 KH :7.73
11/11 16:01:18 W.121 %0 KH :7.74
11/11 18:12:24 W.121 %0 KH :7.74