KH Alkalinity Monitor with AIM

[dpassar12]

Anyone tried this? Opinions? 

[Origami]

No experience with it here. The science is pretty sound, so long as the pH probe remains calibrated and a quality reference titrant is used. However, here's the question that I'd have. At $600, it's a monitor, not a controller. The difference is that it will report out total alkalinity results, leaving it to you to correct it as necessary using other systems or do it manually. If using other, automated systems, you have to find a way to get the data from the KH reading into that target system (that is, to integrate the two systems).  So, for $600 you basically get an automated tester. Once you get dialed in, you're probably only testing alkalinity (at most) once a week. For $50 you can get a Hanna Checker with the first 25 tests included. Reagent for 25 additional tests cost $8 from BRS. That $600 convenience comes at the equivalent cost of over 33 years worth of monitoring tests, and you'll still have to periodically calibrate (and replace) the probe. So, is that enough value to justify the early-adopter premium? Or do we wait to see if the price will drive down as convenience and capability improve?

[dpassar12]

There is a pretty good writeup on r2r, about 44 pages. I am only interested in the monitor/tester not the doser. The monitor with the AIM module to hook up to my apex is 569. This gives the ability for a DKH tile in Fusion, Once that is achieved I can fine tune my CR based off my DKH # which is auto tested every 4 hrs. While I am not a huge fan of spending money I have to consider the $$ of coral in my system vs the cost of this, I already have a hanna checker which I use every other day. I also have other ALK tests that I test the hanna checker against. My biggest issue with any test is the human error factor, 1 or 2 drops less of salt water in a 10 ml sample  can have a significant impact to the accuracy of a test. It would also be nice to get a warning when my ALK is outside of my parameters. That alone may be worth the cost. 

 

Anyway, I gave it to myself as a combo gift for Xmas and my 50th bday. Just not telling the wife how much it is, LOL.  After I set it up, probably after the holidays I will post my thoughts/observations/opinions, good or bad.  The refills are 35 for about 2 months of tests 4x a day. Not crazy about that, so this needs to be a real tool to justify that cost, not just some eye candy... 

[Origami]

One or two drops in a 10 ml sample vial is only 1/2 to 1 percent error. Alkalinity precision of 0.1 dKH is meaningless, practically speaking. Especially if you consider that the central tool here, the pH probe, will drift over time. (Keep it calibrated!) For example, right now, I have to go back and calibrate the probe on my Apex having noticed it's probably off by a good half-a pH point.... Anyway, have fun. I like good toys just like the next guy. Heck, in the last two months, I've picked up a drone and a new 3D printer, and have been playing with both. So, yeah, I'm guilty of indulging. 

 

If you get the chance, look up Randy Holmes-Farley's article titled "A DIY Alkalinity Test Kit." It's basically that test procedure that's being automated here. Note however that the approach measures total alkalinity. It does not distinguish between carbonate alkalinity (which is what we're interested in) and, say, borate alkalinity. Neither do most of our other test kits (however, Seachem has a kit that helps separate the two so you can get a more accurate reading of carbonate alkalinity).

[gws3]

I have a few of the KH monitors. I have SPS dominant systems that consume 2 dkh or more a day. I used to test the alkalinity on each system every other day. Now that the monitors have been running for a few months and I have confidence in how they work I test every two weeks or as needed.

 

They are a little quirky at first. They have incredible precision but poor accuracy. But they do have an offset value you can adjust for accuracy, so once you sample it against your trusted test kit a number of times it will perform very reliably.

 

I have them set to test every 4 hours. For while I ran one every hour. This was interesting because it showed just how precise and repeatable they are and also showed my that I have a very clear diurnal alk swing.

 

I do worry about replacement parts and if they ever stop making them how I will get reagent.

 

But for the amount of money I have invested in corals they make sense for me. If the alk starts drifting due to equipment failure or whatever I will know MUCH faster than I would by hand testing. It will also give me more peace of mind when I take vacation, for alk almost always swings a good bit in a week left unchecked. And overall they save me time.

 

They now come with the AIM so they will plug into any controller in a ph port. You can also get a wireless bridge for less than $20 to make them wireless.

 

As Tom mentioned they require a calibrated ph probe so there is some maintenance there. However if you test with another alk kit every few weeks this should prevent any issues from the probe drifting enough to cause problems.

[dpassar12]

Good to hear you like them, hopefully I have the same experience. The cost is high but compared to what I have invested in my heavy SPS tanks it's pretty small. I really hope that I can dial my CR in much tighter when I have it in fusion.  

[Origami]

I have a few of the KH monitors. I have SPS dominant systems that consume 2 dkh or more a day. I used to test the alkalinity on each system every other day. Now that the monitors have been running for a few months and I have confidence in how they work I test every two weeks or as needed.

 

They are a little quirky at first. They have incredible precision but poor accuracy. But they do have an offset value you can adjust for accuracy, so once you sample it against your trusted test kit a number of times it will perform very reliably.

 

I have them set to test every 4 hours. For while I ran one every hour. This was interesting because it showed just how precise and repeatable they are and also showed my that I have a very clear diurnal alk swing.

 

I do worry about replacement parts and if they ever stop making them how I will get reagent.

 

But for the amount of money I have invested in corals they make sense for me. If the alk starts drifting due to equipment failure or whatever I will know MUCH faster than I would by hand testing. It will also give me more peace of mind when I take vacation, for alk almost always swings a good bit in a week left unchecked. And overall they save me time.

 

They now come with the AIM so they will plug into any controller in a ph port. You can also get a wireless bridge for less than $20 to make them wireless.

 

As Tom mentioned they require a calibrated ph probe so there is some maintenance there. However if you test with another alk kit every few weeks this should prevent any issues from the probe drifting enough to cause problems.

 

Great feedback. BTW, I know when my alk is getting low when my the diurnal swing in pH gradually follows a downward trend because my kalk reactor is running low. 

[scott711]

I have a few of the KH monitors. I have SPS dominant systems that consume 2 dkh or more a day. I used to test the alkalinity on each system every other day. Now that the monitors have been running for a few months and I have confidence in how they work I test every two weeks or as needed.

 

They are a little quirky at first. They have incredible precision but poor accuracy. But they do have an offset value you can adjust for accuracy, so once you sample it against your trusted test kit a number of times it will perform very reliably.

 

I have them set to test every 4 hours. For while I ran one every hour. This was interesting because it showed just how precise and repeatable they are and also showed my that I have a very clear diurnal alk swing.

 

I do worry about replacement parts and if they ever stop making them how I will get reagent.

 

But for the amount of money I have invested in corals they make sense for me. If the alk starts drifting due to equipment failure or whatever I will know MUCH faster than I would by hand testing. It will also give me more peace of mind when I take vacation, for alk almost always swings a good bit in a week left unchecked. And overall they save me time.

 

They now come with the AIM so they will plug into any controller in a ph port. You can also get a wireless bridge for less than $20 to make them wireless.

 

As Tom mentioned they require a calibrated ph probe so there is some maintenance there. However if you test with another alk kit every few weeks this should prevent any issues from the probe drifting enough to cause problems.

 

Which one do you have?  Can you post your experiences?

[gws3]

Good to hear you like them, hopefully I have the same experience. The cost is high but compared to what I have invested in my heavy SPS tanks it's pretty small. I really hope that I can dial my CR in much tighter when I have it in fusion.  

 

It will definitely help. I feel the same way, I have so much $$$ invested in SPS, if this prevents an alk swing that kills a few high end frags it's worth it.

 

I'm planning on using it to transition from 2 part to Ca Rx. I was too nervous to do this before worrying about a big alk swing. Being able to test alk every hour will make it much easier.

 

Great feedback. BTW, I know when my alk is getting low when my the diurnal swing in pH gradually follows a downward trend because my kalk reactor is running low. 

 

Right, I notice the same trend. The only issue that complicates it for me is a lot of tanks in my basement, if I am not pumping in fresh air the pH will trend lower due to increased CO2 in the ambient air. So I don't think I am able to assess alk levels accurately based on pH alone.

 

Which one do you have?  Can you post your experiences?

 

I have three of the KH Guardian Monitors. One is for the newer system and not set up yet, no need since alk consumption is very low. I have one on my 300DD and one on my older system, which has really just become some frag tanks plumbed together. I plan to replace this system with a large display tank in a few years.

 

Did you have any specific questions? I thought I did post my experience, but perhaps my fragmented thoughts weren't clear.

 

I can say in the time I have had them running my alk has not gone over 8 nor dropped below 7.  I target 7.5-8.

 

Maybe this chart will help illustrate the benefit. This is when I had it set to test every hour on my 300DD. Please keep in mind I was still figuring out the correction factor so the y-axis is off by 1.8. This is my biggest gripe about them, how far off the accuracy is. But once you put in the adjustment factor they seem to be very repeatable, and will match my hannah checker very closely.

 

You can see my ~0.3 dkh diurnal alk swing. Also, I think one can conclude the precision of these is better than .1 dkh, probably around .05 dkh. I say this because the readings are not jumping around at all, they follow the trend very closely.

 

[scott711]

They are a little quirky at first. They have incredible precision but poor accuracy. But they do have an offset value you can adjust for accuracy, so once you sample it against your trusted test kit a number of times it will perform very reliably.

 

Graham-  This is what I was referring too. 

[Origami]

Right, I notice the same trend. The only issue that complicates it for me is a lot of tanks in my basement, if I am not pumping in fresh air the pH will trend lower due to increased CO2 in the ambient air. So I don't think I am able to assess alk levels accurately based on pH alone.

 

Good point. I pull fresh air all the way down from a pick up point just outside my attic and into a manifold for distribution to my skimmer. However, unless the CO2 level varies a lot in your basement (like from shifting occupancy), then you shouldn't see a trend - just an overall lower pH. When my kalk is exhausting, I'll see the diurnal swing of some regular magnitude slowly shift downward over several days time - sort of like a sinusoid riding on a downward-sloping ramp. But, you're right, if you've got variable CO2 in the environment, then having access to fresh air can help stabilize the pH so you can view the effect of declining alkalinity without a direct measurement.

 

You can see my ~0.3 dkh diurnal alk swing. Also, I think one can conclude the precision of these is better than .1 dkh, probably around .05 dkh. I say this because the readings are not jumping around at all, they follow the trend very closely.

 

I find this interesting. This swing could be due to a cycle of corals building skeleton. The diurnal swing that we normally observe in pH is due to shifting concentrations of dissolved CO2 in the water. That is, at night, coral cells breathe, taking in oxygen and releasing CO2. That increases the dissolved CO2 in the water and drops pH. During the day, the corals shift to photosynthesis which takes up dissolved CO2 and release oxygen. This decreased the dissolved CO2 and raises pH.  However, that raising and lowering of CO2, while it shifts pH, does nothing to increase or decrease carbonate alkalinity. 

 

So this (is intriguing and) makes me wonder: Is what you're seeing really an alk swing or is it really just the shift in the pH titration curve that this method relies upon to measure alkalinity. If you dosed only during the night and not during the day, would you see an "increase" in alkalinity? If so, it's the curve shifting, not the alkalinity shifting.

 

You see, this method of titrating to determine alkalinity relies on finding the "knee" in a titration curve. That curve can shift depending upon the level of dissolved CO2. If the algorithm that these devices relies on reaching a target pH, then the amount of titrant used can vary (just a little) depending upon the level of dissolved CO2 in the sample. If, however, we were to take multiple samples (i.e. add titrant - measure - add more - measure - add more - measure, etc.) and then run a curve fitting algorithm, we might be able to determine where the knee was and begin to compensate for the diurnal variance in dissolved CO2 and get a more accurate measurement of total alkalinity in the water sample.

 

Sorry, getting off topic....

[gws3]

Check this out Tom, this may help you figure it out. I think there really is a diurnal alk swing. Notice the alk and ph are out of phase. The alk starts dropping towards the end of my photoperiod. Let me know what you think.

 

[gws3]

So what I meant Scott is that you have to get the unit up and running consistent, then take a number of measurements against the test kit you trust the most. Find the difference for each and then average it. You plug this into the offset setting box, and from their on out it will read very consistently with your test kit. For me Hannah Checker, Salifert and Lamotte titration test kits all test very close. But the two guardians I have up and running are about 1.5 and 2 dkh off. But once I accounted for this offset (poor accuracy) it seems to test spot on with these other kits every time (good precision).  Let me know if any of that didn't make sense. I think you can see from the charts above how precise it is. If it wasn't precise the chart would have lots of noise, not follow a smooth ramp up and down like it does.

 

Graham-  This is what I was referring too. 

[dpassar12]

Do you let the test water back into your system or do you collect it?

[gws3]

At first I ran it into the skimmer collection cup. Now on one system I have it running back into the sump. I think the reagent is likely just a common acid, so I don't think there's too much to worry about.

[Origami]

Check this out Tom, this may help you figure it out. I think there really is a diurnal alk swing. Notice the alk and ph are out of phase. The alk starts dropping towards the end of my photoperiod. Let me know what you think.

 

 

Interesting, Graham. Something to think about. It doesn't agree, though, with some papers that I read about a decade ago that spurred a lot of discussion on various forums (here, Reef Central, and other places). 

 

Back then, I read a paper (or two) that indicated that most stony coral growth occurred in cycles tied to the photoperiod (lighting schedule). But those papers indicated that most growth occurred 8-10 hours AFTER the lights went out. If your alkalinity drop was due to calcium carbonate deposition, then the start alk drop should be seen about 8-10 hours after the pH started plummeting (which is likely because your lights were turned OFF). Instead, what I'm seeing in your charts is that your alkalinity drop is happening roughly 4 hours after your lights go ON. So something else is going on with the measurement.

 

See this thread (from 2012) and this one (from 2009). Basically, and what you may find useful (or may already know since it looks like your lights are on for about 8 hours) is that many people found that their corals grew faster with shorter light cycles (6-8 hours) back then.

 

Great graph!

[gws3]

Not sure what to think then without doing some more reading.

 

Maybe I'll get my third one hooked up this week on the my new system. There is close to zero alk demand on that system since it is new and only has some test frags in it. But there is a diurnal pH swing. If the diurnal alk swing is present in the plot we can assume it's due to something other than the alk actually changing through the day. If it's not present in the plot perhaps it is the case on the established systems.

 

Yeah I run shorter photoperiods as well. Metal halides usually only on for 6 hours. 5 hours for the ones on the 300 as I added another pair of T5s and a reefbrite xho blue.

[Origami]

Not sure what to think then without doing some more reading.

 

Maybe I'll get my third one hooked up this week on the my new system. There is close to zero alk demand on that system since it is new and only has some test frags in it. But there is a diurnal pH swing. If the diurnal alk swing is present in the plot we can assume it's due to something other than the alk actually changing through the day. If it's not present in the plot perhaps it is the case on the established systems.

 

Yeah I run shorter photoperiods as well. Metal halides usually only on for 6 hours. 5 hours for the ones on the 300 as I added another pair of T5s and a reefbrite xho blue.

 

The diurnal pH swing is due to photosynthesis, so if you have macroalgae or any algae in the system, pH should elevate during the day and decrease at night when the plant cells move toward respiration. If you simply stopped any alk dosing for a short time, then any rise in the alkalinity measurement would be suspect assuming no other outside sources of alkalinity are introduced (e.g. non-RODI top off water).

[gws3]

That's what I'm getting at. I have a doser on but it is only dosing about 0.1 dkh a day because there are just a few frags in that system. Basically the alkalinity is constant.

 

So if the kh monitor shows a diurnal swing on that system it is likely just due to the pH diurnal swing effecting the reading.

 

If there is no diurnal alk swing, that we can likely conclude that the diurnal alk swing I am seeing on my other two systems is actually the alk going up and down each day.

 

The diurnal pH swing is due to photosynthesis, so if you have macroalgae or any algae in the system, pH should elevate during the day and decrease at night when the plant cells move toward respiration. If you simply stopped any alk dosing for a short time, then any rise in the alkalinity measurement would be suspect assuming no other outside sources of alkalinity are introduced (e.g. non-RODI top off water).

[Origami]

That's what I'm getting at. I have a doser on but it is only dosing about 0.1 dkh a day because there are just a few frags in that system. Basically the alkalinity is constant.

 

So if the kh monitor shows a diurnal swing on that system it is likely just due to the pH diurnal swing effecting the reading.

 

If there is no diurnal alk swing, that we can likely conclude that the diurnal alk swing I am seeing on my other two systems is actually the alk going up and down each day.

 

That's reasonable. However, the third system will also have to show evidence of a pH swing as well as an alkalinity swing, when there's little to no consumption of alkalinity in that system. I think this is what you're getting at, so I think we're on the same page. It would be interesting to see what you measure.

[dpassar12]

Ok so I installed my new KH Monitor Pro on the 27th tuned the dKH to avg Hanna and Salifert over several tests. Today I installed AIM so my Apex can control my CR. Installation on both products was pretty easy. There are videos that walk you through both installations. Initial install of Monitor took about 1.5 hours to install and complete running of tests. The AIM installed in 20 minutes including coding for my CR. So far I give it an A. If it can keep my ALK between 9.5 and 10 I will give it an A+... 

 

I also installed a APEX DOS for AWC. I will give this a B+. Works great but it is LOUD very LOUD. Right now I have it set to change 2 gals everyday. 1 gal at 9 am and 1 gal at 6 pm. It can change up to 30 gals in a day. I like the fact that you can see how many MLs it swaps out on tiles in fusion. At some point I will add a float switch to alert me when I need to refill my saltwater but that can wait for now, I always have 30+ gals of SW made.  

[John Ford]

Do you turn your ato pump off, remove one gallon, then add a gallon during your AWC? Or Add a gallon and then remove a gallon so your float doesn't turn your ato on?

[dpassar12]

It does both at the same time.  I am removing water from a frag tank and pumping the fresh saltwater into the overflow of the same tank. My ATO does not trigger. Also the DOS pumps do not remove all the water at one time. They run in 5m intervals over the course of an hour or so. Now that is working smoothly. I am going to increase to 4 gallons a day. That will bring me up to approx a 4% water change every week.  

The KH monitor is a game changer for me. I have been trying to dial in my CR for 2 years. This has done in a week. Turns my CR on at dKH 9.5 and off at 9.8. It has been spot on with Salifert and Hanna every time I have double checked it the number. Great tool for a large system or a system with a lot of $$$ SPS.  Anytime you want to come up at check them out John, or anyone else, just send me a pm. 

Edited December 31, 2017 by dpassar12

[gws3]

I finally got the KHG Monitor installed on my other system. The monitor indicates a daily alk swing. However, alk consumption has increased on this system, so I am not sure I can conclude with any confidence whether or not the reported alk swing is true or a result of the dirunal pH swing and how the tester works.

 

In other exciting news Scott and I have been looking into a substitute acid for the manufacturer's reagent. By measuring the volume of test water, the volume of reagent added and the resulting alk reading I have been able to back calculate the normality of the acid they use. I plan to do some testing with HCl this weekend.

 

This is exciting because the cost to make reagent will drop from $35 to less than a dollar. At this cost point I can justify running tests at the maximum rate, every hour. This will make me feel much better about paying the introductory price for the monitors.

 

[Origami]

I finally got the KHG Monitor installed on my other system. The monitor indicates a daily alk swing. However, alk consumption has increased on this system, so I am not sure I can conclude with any confidence whether or not the reported alk swing is true or a result of the dirunal pH swing and how the tester works.

 

In other exciting news Scott and I have been looking into a substitute acid for the manufacturer's reagent. By measuring the volume of test water, the volume of reagent added and the resulting alk reading I have been able to back calculate the normality of the acid they use. I plan to do some testing with HCl this weekend.

 

This is exciting because the cost to make reagent will drop from $35 to less than a dollar. At this cost point I can justify running tests at the maximum rate, every hour. This will make me feel much better about paying the introductory price for the monitors.

 

Great news on the search for a second-source reagent. I'm assuming that you'll use a laboratory grade acid and not hardware-store grade muriatic acid. Is that a fair assumption? I've never really tested the hardware store stuff for consistency or purity. I suspect that it's reasonably well-controlled and may suffice as a source, but that's just an opinion.