adjusting CA reactor

[jelwyoming]

I just about have my CA reactor balanced to maintain alkalinity, but with that set, I am still loosing ground on CA. Will increasing my bubble rate and decreasing the flow increase the calcium content of the effluent?

[Randy Holmes-Farley]

Don't adjust it to mess with calcium. If you are using calcium carbonate, and it is maintaining alkalinity (without any other pH additives or buffers) then it should also be maintaining calcium. If not, the calcium is likely being lost in other ways, like water changes with a low calcium mix, or just inaccurate testing.

[jelwyoming]

Thanks Randy,
I was hoping that was the right answer. What kind of error would you normally expect? I have two kits; a Seachem and a Salifert. The Salifert shows 3.56meq/l, while the Seachem shows 4.5meq/l. I ran the tests 3 times on each brand, with the same results on all 3 tests. The resolution of the Salifert test is better in 100ths of a meq, while the SeaChem is in 10ths, that doesn't necessarily mean that the test is more accurate. Any experience in that regards?

[Randy Holmes-Farley]

Alkalinity kits usually vary a lot less than calcium kits, but even alk kits can be off.

Which Seachem alkalinity kit? I tested the total alk kit that came with the borate alkalinity kit and it was perfectly accurate when I tested it.

[jelwyoming]

This was the one with just total alkalinity.
I did an experiment last evening trying to nail this down a bit..rather crude, but I suspect that part of my measurement errors come from the fact that the seachem kits rely on a sample bulb where the measurement of the sample is not real accurate. I found that portions of the sample remained in the tube. Also there was some variance in what is the "base of the bulb". I think seeing those points and comparing it to the repeatabliliy of the Salifert sample syringe, indicate possilby where my errors are from.
I put 10 grab samples in a container to multiply the error, marked the level and repeated it to see if I came up with a variance. The syringe was much more repeatable.
Perhaps, the sample measurement and the indicator drop size (this seemed to vary some as well) are not real critical to the results of the test?