KH Guardian: Automatic Alkalinity Controller- My Experiences

[Rick.45cal]

I can't wait for the new PCB!

 

[eltonw]

I initially was planning to dump right back into the tank. Then I read everyone was dumping into a waste container instead. This makes me more comfortable dumping back into the tank when my tank is ready.

I dump the tested sample water back to tank about 3.5 years already. I did not any problem at all.

 

[eltonw]

I can't wait for the new PCB!

????? You should ask Coralvue about it.

 

[DP REEF]

I just switched to dumping in tank. Didn't have an easy way to offset the saltwater taken out..... my salinity would drop during the week by .3

 

[Jonty]

I can't wait for the new PCB!

No Doubt but it is not available in USA yet

 

[eltonw]

No Doubt but it is not available in USA yet

New PCB is under producing now. And it will arrive US may in next week.

AIM mass production will start around end of Apr. So currently all distributors are gathering the order now.
So user can contact them for your demand.

 

[DavidUK]

This isn't rocket science. It is simple chemistry. No, it does not massively change. It changes so minimally you can hardly detect it. It effectively adds a tiny extra boost to alkalinity demand. In your example, 480 ml per day in a 100 liter tank boosts the apparent alk demand by 0.03 dKH. The pH effect is minimal. If aeration is complete, there will be no pH effect. If aeration is less than complete, the effect is small. I have shown that depleting alk by 1.4 dKH (with hydrochloric acid) instantly drops the pH by about 1.19 pH units. You are talking about 40 times less and spread out over the day. I'd be surprised if you could detect more than 0.02 pH unit drop in average pH.

We discuss these effects extensively in a thread in the chemistry forum with all of the folks that make the various automated alk devices. I might toss the waste too, but in reality it is not going to be a concern.

Many thanks for the reply - much appreciated!! Please do not think I was questioning you at all - I am merely trying to understand! I will have a look over the thread you linked to.

I guess I incorrectly made an assumption that additions to the tank would have a cumulative effect?

Following the above along, if the 480mls a day is added to the 100 litre tank for 10 days, the net result is the overall alk demand is still only pushed up by 0.03kH, not 10 x 0.03kh?

 

[Randy Holmes-Farley]

Many thanks for the reply - much appreciated!! Please do not think I was questioning you at all - I am merely trying to understand! I will have a look over the thread you linked to.

I guess I incorrectly made an assumption that additions to the tank would have a cumulative effect?

Following the above along, if the 480mls a day is added to the 100 litre tank for 10 days, the net result is the overall alk demand is still only pushed up by 0.03kH, not 10 x 0.03kh?

Yes, over 10 days the alk depletion effect (not the pH effect) is 10 times higher. The pH effect is not cumulative. In essence, you are just adding a little extra CO2 each time, and it requilibrates with the air.

What exactly happens in the long run depends on many factors, such as water changes, tank consumption changes, and how accurately you deliver alkalinity. I wouldn't be surprised if 0.03 dKH per day is smaller than the growth rate of the alk demand in an SPS tank anyway. So you need to keep on top of the constantly increasing alk demand in such tanks if you want super precise control over dKH.

 

[Randy Holmes-Farley]

FWIW, sending the tested tank water to waste does not necessarily solve this alk creep problem. If you do not replace it with new seawater in exactly the same amount, the alkalinity is depleted the same. So an ATO, for example, will replace the used tank water with zero alk RO/DI, and the net loss of alk to the system is exactly the same as returning the water to the tank. Only if you add back seawater with normal tank alk will you not see this drop. You also have a slow salinity drop if you send the water to waste. You then can correct both the salinity and alk drop by adding back an appropriate amount of seawater.

 

[JimWelsh]

Believe me I weighed it out with a scale that measures to .01

And, of course, since you are being so precise, @Sps3Sixty, you also compensated for the effect of the buoyancy of air, correct? If not, then you likely weighed out appx. 1501.58 grams of water (assuming an ambient temperature of 25C), and not 1500.00 grams. In order to get 1500.00 grams of True Mass when weighing pure water on a balance calibrated with stainless steel weights, at 25C, you would need to weigh out a Conventional Mass of 1498.42, plus or minus a little, depending on relative humidity, barometric pressure, and elevation (factors which affect the density of air). Reference: https://www.nist.gov/document-13101

 

[DavidUK]

FWIW, sending the tested tank water to waste does not necessarily solve this alk creep problem. If you do not replace it with new seawater in exactly the same amount, the alkalinity is depleted the same. So an ATO, for example, will replace the used tank water with zero alk RO/DI, and the net loss of alk to the system is exactly the same as returning the water to the tank. Only if you add back seawater with normal tank alk will you not see this drop. You also have a slow salinity drop if you send the water to waste. You then can correct both the salinity and alk drop by adding back an appropriate amount of seawater.

Thanks for this clear answer!

So it actually seems for the KHG (assuming the acid source is pure) that the addition back to the tank is in some ways desirable, in fact preferable?
1. Option 1 waste taken away - Small decrease in alkalinity BUT decrease in salinity (in my example of testing every hour in a 100 litre tank - this would mean 480ml/day of seawater is replaced with RO water, so a 0.48% reduction in salinity each day, so after 10 days, approx 5% reduction in salinity)?
2. Option 2: Add waste back to tank - same small decrease in alkalinity as in 1, but that is all.

So, to me it looks like option 1 is the "best" option?

 

[DavidUK]

Thanks for this clear answer!

So it actually seems for the KHG (assuming the acid source is pure) that the addition back to the tank is in some ways desirable, in fact preferable?
1. Option 1 waste taken away - Small decrease in alkalinity BUT decrease in salinity (in my example of testing every hour in a 100 litre tank - this would mean 480ml/day of seawater is replaced with RO water, so a 0.48% reduction in salinity each day, so after 10 days, approx 5% reduction in salinity)?
2. Option 2: Add waste back to tank - same small decrease in alkalinity as in 1, but that is all.

So, to me it looks like option 1 is the "best" option?

Actually, I meant option 2!

 

[Randy Holmes-Farley]

Best option is to either:

1. Send tested water to waste and automatically add back same amount of new salt water

or

2. Send tested water to tank and automatically add appropriate amount of alk to tank.

 

[JonasRoman]

I must say something who has tested option : send test water to waste canister and only have a observing look at the salinity:
you are exaggerating the issue. It is absolutely no issue or problem or even difficult at all with this very very slow and minimal decreasing salinity. Believe me, I have tested that option for 6 months and it is so extremely small amounts of salt you export so you can with no demand of precision at all only put some salt in the osmosis tank to the ATO and that is fine.
Of course it is easy to incorporate another pump to pump saltwater back but that add another hoses, canisters and works with mixing saltwater.
Keep this simple. It is no issue. Just put some salt in the ATO and have a little check on the salinity and I promise, that will work with enough precision and no extra work and no extra equipment
Besides that: if you run Balling we have in same way a slight increase in salinity so for these user the decreasing of salinity due to water testing will be even less or maybe total compensated by the Balling caused increase if salinity. Another reason of to not lay energy in saltwaterpumps etc.
This is simply a question you do not have to worry about.

 

[Randy Holmes-Farley]

I must say something who has tested option : send test water to waste canister and only have a observing look at the salinity:
you are exaggerating the issue. It is absolutely no issue or problem or even difficult at all with this very very slow and minimal decreasing salinity. Believe me, I have tested that option for 6 months and it is so extremely small amounts of salt you export so you can with no demand of precision at all only put some salt in the osmosis tank to the ATO and that is fine.
Of course it is easy to incorporate another pump to pump saltwater back but that add another hoses, canisters and works with mixing saltwater.
Keep this simple. It is no issue. Just put some salt in the ATO and have a little check on the salinity and I promise, that will work with enough precision and no extra work and no extra equipment
Besides that: if you run Balling we have in same way a slight increase in salinity so for these user the decreasing of salinity due to water testing will be even less or maybe total compensated by the Balling caused increase if salinity. Another reason of to not lay energy in saltwaterpumps etc.
This is simply a question you do not have to worry about.

I don't disagree with that, and I don't think I exaggerated the effect. I didn't say anything at all about the magnitude, but it is easy to determine.

480 mL per day removed from a 100 L tank (obviously it depends on tank size) will drop salinity by 0.48% per day, or 0.17 ppt out of 35 ppt. A little salt in an ATO is a fine offset, and is exactly what I recommended in best option 1.

 

[klp]

Worked my way through this excellent discussion. Very informative in the discussions on alkalinity and ph aside from the hardware. Thank you Rick.45cal for starting it and for all the contributors.

If I understand Rick.45cal correctly you use it only to monitor alkalinity not actually add anything in. Is that correct? If so then it seems to be just an expensive tester. I understand why it works well for your situation but wonder what benefit it provides to most reefers that cannot be done with Salifert etc other than convenience.

 

[klp]

As there were some concerns about accuracy how about the company putting out a reference fluid that would be exactly 8.0 or 7.6 or whatever so the equipment could be checked against the sample? If I pay $1000 for equipment I want to know that it works out of the box without having to cross check it with other test equipment. I am not convinced that DIY solutions could be nearly accurate enough to use as a cross checker for all but a very few if any.

 

[JonasRoman]

I don't disagree with that, and I don't think I exaggerated the effect. I didn't say anything at all about the magnitude, but it is easy to determine.

480 mL per day removed from a 100 L tank (obviously it depends on tank size) will drop salinity by 0.48% per day, or 0.17 ppt out of 35 ppt. A little salt in an ATO is a fine offset, and is exactly what I recommended in best option 1.

Then we think same. I did not ment exactly you was exaggerating, but more generally the concern about this subject

 

[CoralWealth]

I know there are other companies currently trying to make their own verision of this but you actually think they will have them out by the end of this year? I also am wondering if a company will just make a monitor and not a monitor and controller, would be a lot cheaper

 

[Rick.45cal]

@codydemmel4 The makers of the KHG have a monitor only coming out as well.

@klp I'm only using it's dosing feature, at the moment, as a way for me to tell when my alkalinity consumption has increased in the tank, when it drops below the set point (my bottom threshold) then the KHG doses and I know I need to kick my dosing up slightly. It's just the way I have been running it and have been very happy with how it is working. Everytime I check my calcium level it is right where I left it so I'm not falling behind. Maybe once the new printed circuit boards become available I'll change my strategy and see if letting it fine tune my alkalinity makes it more stable. I've generated enough data points at this point the current way I've been using it to have a pretty good understanding of what my daily alkalinity swing is in the tank. (generally over the day it's between .2 and .3 dKH, if I'm dosing ahead of the KHG setpoint).

I'm still exploring how to best use it as a tool. (For my needs)