Can't get Alk dosing correct - what am I missing?

[jkobel]

I have been using an Apex and BRS dosers for about 2 years and still cant seem to get this right.

Today, i am dosing about 52.8ml of two-part Alk mix daily (two weeks ago raised it from 36.3ml/daily) and I'm not able to keep the levels stable. However, my math tells me I'm dosing correctly.

A few months ago i shut down the dosers and watch the levels drop for a week to get a sense for what was actually getting consumed. I took the daily average consumption and set my dosers based on that - it didnt work.

Then, while still dosing and readings dropping similarly to what is in the graph below, I did the same calculation to come up with what i thought i needed to add additionally and increased the dose to what I'm at today. The consumption is still higher than the dose.

What am I doing wrong? Is the math broken or am I not considering a variable?

Thanks.

system is 140 gal
ph-7.88
alk - 6.06
ca - 423
mg - 1360
sal - 1.025

 

[Naekuh]

Have you tried a manual test with a different tester?
Sometimes Trident at the last bit of reagent can give out false results.

 

[jkobel]

yes, I've been checking everything with Hanna. Been testing with Hanna 3 times and averaging the results. Also been calibrating the trident against the tank water to remove another faulty input

 

[topjimmy]

Are you dosing into a high flow area, and at different times for ALK and Cal?

 

[KStatefan]

Have you verified you are getting 52.8 ml from your doser?

 

[Randy Holmes-Farley]

Is the apex controlling the dosing pump?

No matter what else is happening, an automated system ought to just keep pumping in alk supplement if it thinks alk is low.

 

[Js.Aqua.Project]

In line with what Randy said, I would let the Apex help you via the Trident (trust but verify).

You could add a line to the outlets for the Alk doser that is something like:
If AlkxY > Z then OFF

Replace Y with the number for your Alk input (for example mine is Alkx5) and replace Z with your target value +.1 (ex target 8 set to 8.1) so that it will shut off any time it goes over that it will turn off while leaving you a slight buffer as it falls.

Then set your dosers to be ~10% more than you think and it should help.

What two-part are you using?

 

[jkobel]

Are you dosing into a high flow area, and at different times for ALK and Cal?

yes, into the return chamber, offset by 9 hours

 

[jkobel]

Have you verified you are getting 52.8 ml from your doser?

calibrated it 2 weeks ago, I was certain this was the issue but its correct

 

[jkobel]

Is the apex controlling the dosing pump?

No matter what else is happening, an automated system ought to just keep pumping in alk supplement if it thinks alk is low.

Its controlling them via a timer program, not based on the reading.

I actually was unaware that the Apex could do that with BRS dosers, I thought it needed the Neptune Dos pumps for that.

 

[Randy Holmes-Farley]

calibrated it 2 weeks ago, I was certain this was the issue but its correct

Not sure what you are saying.

Why is that magic number important? Perhaps you need 60 mL/day?

 

[Acros]

Alk consumption goes up overtime. How confident are you about the calibration of said BRS dosing pumps? As far as I know, there is no way to calibrate BRS dosing pumps.

I am assuming that you test at the same time every time.

 

[Js.Aqua.Project]

Its controlling them via a timer program, not based on the reading.

I actually was unaware that the Apex could do that with BRS dosers, I thought it needed the Neptune Dos pumps for that.

With the Apex, any outlet can be programmed to watch other outlets and inputs because it is all If This Then That (IfTTT) programming.

For example, I have a virtual outlet for my lights as there are 5 and they are all programmed to watch that one outlet; if that outlet gets turned off, they will all turn off.

I do the same thing with an virtual outlet called "Maintenance" if I need to do a deep cleaning in the tank I can turn that one outlet off and the skimmer, return, and powerheads will all turn off together.

So in this case you would want the outlets/outputs the dosers are plugged in to to watch the input for the corresponding test, ie.; Alk doser watches the Alk input from the Trident while a calcium doser would watch the Ca input.

 

[vabben]

I have been using an Apex and BRS dosers for about 2 years and still cant seem to get this right.

Today, i am dosing about 52.8ml of two-part Alk mix daily (two weeks ago raised it from 36.3ml/daily) and I'm not able to keep the levels stable. However, my math tells me I'm dosing correctly.

A few months ago i shut down the dosers and watch the levels drop for a week to get a sense for what was actually getting consumed. I took the daily average consumption and set my dosers based on that - it didnt work.

Then, while still dosing and readings dropping similarly to what is in the graph below, I did the same calculation to come up with what i thought i needed to add additionally and increased the dose to what I'm at today. The consumption is still higher than the dose.

What am I doing wrong? Is the math broken or am I not considering a variable?

Thanks.

system is 140 gal
ph-7.88
alk - 6.06
ca - 423
mg - 1360
sal - 1.025

Pretty simple...Just increase your daily dose until you get to the level you are trying to achieve. No math needed, just up your dose and test.

 

[jkobel]

Not sure what you are saying.

Why is that magic number important? Perhaps you need 60 mL/day?

Agreed, I'm not worried about the number itself. I'm struggling to figure out how to calculate how much to actually dose since they way i'm calculating it now isn't working.

I can just keep raising it until it hits equilibrium but I want to understand why its not working as expected.

 

[Randy Holmes-Farley]

Agreed, I'm not worried about the number itself. I'm struggling to figure out how to calculate how much to actually dose since they way i'm calculating it now isn't working.

I can just keep raising it until it hits equilibrium but I want to understand why its not working as expected.

How are you calculating the need? You may be calculating how much is needed to bump back to your target, but then there is more consumption before it gets there, and you never make it. . Just keep upping the dose until alk stabilizes, and if that dose seems excessively high (in dKH per day), then try to determine if precipitation (hardening of sand, etc.) is causing it to be too high.

 

[Borat]

You cannot estimate alk accurately based on how much it drops over a significant period of time. when alk is high (say 8) consumption is high and when it drops toward 6 consumption almost stops, so its a upward sloping curve (that bends towards alk of 6). You could easily be out by a 2x-3x factor i think..

best way to estimate how much to dose is to increase the dose until alk stabilise at your ideal level. alk of 6 is not the one i would want to have.

 

[twentyleagues]

Agreed, I'm not worried about the number itself. I'm struggling to figure out how to calculate how much to actually dose since they way i'm calculating it now isn't working.

I can just keep raising it until it hits equilibrium but I want to understand why its not working as expected.

I am neither a chemist or mathematician, but for anyone to help you figure out why you dont have the expected outcome they would need your math (basically show your work, I was told this so many times in school lol). I have a set goal in mind for my alk level if I test and its low I increase the dose if it overshoots a bit I decrease it some. I dont have an auto-tester I test manually every couple of days unless I see a significant drop or increase, then I test daily for a couple days. Seems like every time I get comfortable and move to weekly tests it is off more then i'd like.

 

[jkobel]

Alk consumption goes up overtime. How confident are you about the calibration of said BRS dosing pumps? As far as I know, there is no way to calibrate BRS dosing pumps.

I am assuming that you test at the same time every time.

I calibrate these pumps by running it for 30 mins into a cup and dividing the output by 30 to get the rate.

Always test at the same time, yes

 

[KStatefan]

From your charts it looks like it is dropping 0.25 per day increase your dosing by that much and see where you are then.