Limewater CO2 exposure

[matt_rains]

Hi Randy,

Thanks for your contribution to Advanced Aquarist. Your articles are always an interesting read.

I do have a question for you in regards to the article "How to Select a Calcium and Alkalinity Supplementation Scheme".

In the section on Limewater you discuss the use of Nilsen reactors and the traditional reservoir (plastic rubbish bin)

I was under the impression that the unless the reservoir was sealed air tight that it would mix with co2 and reduce the effect of the solution within the first few days. This seems to be one of the key selling points of the Nilsen reactor.

Is this true, if so, what are the parameters and reality wink surrounding this. I am considering using a 50L rubbish bin but the lid is not air tight. I can incorporate some styrofoam to reduce gas exchange but is this really effective.

Best Regards,
Matt

 

[randy holmes-farley]

It is one of the key "selling" points of Nilsen reactors. Unfortunately, it is also almost completely bogus. As far as I know, I've never seen any actual numbers from this posted by anyone except myself. When I measure it myself, the effect is small.

I've become so concerned about the numbers of people getting such reactors for this reason that I'm going to write up me findings into an article shortly.

In summary, the degradation of limewater by CO2 is really quite minimal (unless, of course, you are aerating it or stirring it while open etc.), even though it looks to be significant based on solids forming.

For example, the 44 gallon trash can that I use does not loose any appreciable potency over the 2-3 weeks that I use it. It simply has the normal trash can lid put on it. The same hods true for limewater in a 1 gallon pitcher wide open to the air if there are extra solids on the bottom.

If you are concerned, and really need every last drop of potency, put some extra lime solids into the water, and let them sit on the bottom. They will disoslve if some is lost to reaction with CO2.

By all means use a Nilsen reactor is space is a limiting factor. If not, use a trash can.

 

[danmhippo]

Wow....... I always thought otherwise....

Randy, using trash bins, do you still place a powerhead in there, and kicks it on once a day to keep the kalk saturated like you would with a closed lid kalk reactor?

 

[matt_rains]

I've become so concerned about the numbers of people getting such reactors for this reason that I'm going to write up me findings into an article shortly.

great! I look forward to reading it.

By all means use a Nilsen reactor is space is a limiting factor. If not, use a trash can.

I'm looking at the bin as we speak

Regards,
Matt

 

[randy holmes-farley]

Randy, using trash bins, do you still place a powerhead in there, and kicks it on once a day to keep the kalk saturated like you would with a closed lid kalk reactor?

I used to use a powerhead to stir it when first mixing and then stop. Now I just put the solids on the bottom, and pour in the water in 5-6 gallon buckets. That's plenty of agitation to get it initially saturated (if that is the goal, I don't presently use saturated limewater, but something with less lime in it), and it stays that way.

Right now, for example, I'm running a test for the article. The limewater had a conductivity of 3.8 mS/cm (saturation is around 10 mS/cm) when first mixed a week ago. This morning I measured it again: 3.8 mS/cm. So there has been no noticeable degradation in the past week (the conductivity drops as CaCO3 is formed, taking the conductive ions, Ca++ and OH- out of the solution; in the article I will quantify the realtionship between conductivity and potency in case folks are not readily convinced by conductivity).