Unstable alk using CO2 reactor

[BradR]

Hi,
I’m currently running a Geo 818 calcium reactor with coarse ARM media for a 550gal tank with mostly SPS and can’t get a stable alkalinity.
The reactor gets ~1 bubble CO2 per 2.5 sec and output is 150cc/min fed by a maxi jet that runs continuously.
The CO2 input turns off above 8.1 and back on below 8.1. Mg is ~1290.
Tank alkalinity is measured 4x a day and Ca/Mg twice daily.
Per this pic when the CO2 turns off, alk can stay elevated 18 hours then drops suddenly from 8.17 to 7.6 in 6 hours.
I only care because it’s been hard keeping tenius and this is the only value that’s grossly off after doing an icp test.
A DOS exchanges about 4gal a day with reef crystal salt. The trident seems to be getting adequate samples. Are these values impossible with this setup?

 

[Snoopy 67]

1- what is the alk of new saltwater?
Read this article- IT WORKS

Calcium Reactor Thoughts and Tuning

docs.google.com

 

[Js.Aqua.Project]

If you're using the Trident to help control the CaRx then you're going to have a fluctuating dKH level. You can narrow down the fluctuation by increasing the testing frequency of the Trident but that's about it.

The Apex just sees that input as being in/out of the desired range for the entire time between tests and will not turn in back on/off until the next test is performed. So if you're running the basic 4 test a day cycle that means 6 hours between each on/off.

I am also using my Apex and Trident to help control my CaRx and run the 6/day cycle right now which puts 4 hours between each test.

The drawback of the more frequent tests is having to replace the reagent more frequently. Otherwise I would consider moving up to the 12/day and get a test every 2 hours.

 

[BradR]

Thanks for the link on tuning the reactor. Doubling the alk test frequency from 4 to 8 times a day. Hopefully that’ll shed some light on what’s happening.

 

[jda]

Do yourself a favor and just tune the reactor and let it run 24x7 with constant output. There can be a learning curve, but all of a sudden you will get it and then you will never have any issues again. Using alk devices or pH monitors are all just trouble in the long term.

The only think that you have to test is effluent alk and also tank alk. Salifert is great for since since they are cheap, accurate and can handle alk numbers that get really high.

 

[BradR]

Sounds good. I tripled the time between co2 bubbles and will see where the alk settles. Thanks

 

[Randy Holmes-Farley]

Bear in mind that if you add alk evenly 24/7 and alk is mostly used during the day, the tank alk will not be particularly steady.

Also, if the CO2 is bubble controlled and not pH controlled, you may actually dissolve more and release more alk at night since the pH entering the reactor is already lower, exacerbating the pH dosing vs consumption timing issue.

 

[Randy Holmes-Farley]

This setup calculator may also be useful:

Calcium Reactor Setup Help

 

[BradR]

Thanks for the help guys. The alk swings are like a quarter what they were!