Kalkwasser for RODI fed ATO - Users

NEFFx · Oct 30, 2016

Im not one to post questions, but i havent really found a solution for this and nuked my tank once using Kalk in an ATO, so rather query the crowd.

The Question: Using Kalk in an ATO (8g bucket) that is constantly refilled by RODI. How much kalk to does, If I over dose does it sit at saturation, or is it better if the RODI tops off too much water before I resupply kalk?

I have a 70g reef. mostly frags. I run GFO, Carbon, Biopellets (dosed with Micro Bacter and Fuel), replace filter socks every 4-7 days. pretty standard reef tank IMO.

I run a Spectrapure LF2 ATO (uses water pressure to determine level and doses small amounts frequently, works great). It runs off an 8g trash can that is hooked up with a mechanical float valve from the Spectrapure RODI (output is 0 ppm).

the problem: My KH seems to run quite low around 7 (I do use tropic marine salt which buffers at 7.5) but I would like to keep it around 8-9. I would like to use my doser and it is setup, but last time I dosed some (6x5ml=30 ml a day) which would increase dkh .3 a day. and kh went up to 13.

I wanted to get some ideas from users with a similar setup and how they run kalk. I can be away from my tank for up to a month, so automation is key, was thinking of running an eheim feeder to add kalk to ATO?

Randy Holmes-Farley · Oct 31, 2016

With continuous refill of the ATO reservoir (something I never thought was desirable and I always did manual refill and mixing when it was close to empty), you are basically making an 8-gallon limewater (kalkwasser) reactor, and will have to find a way to mix it to dissolve the solids and the new fresh water coming in.

Are you stirring it?

NEFFx · Oct 31, 2016

I use a pump to stir it about once a day (timer). I feel the frequency doesn't need to be as high since the volume is large compared to a regular kalk reactor, it also alows me to reduce the likelihood of suspended particles getting into the system. As much as I'd like to add new, premixed kalk to the system, its just not feasible with my schedule. My understanding is that the kalk will reach saturation, so it is not possible to overdose? What are your feelings on this. My tank uses about 8g a week.

Randy Holmes-Farley · Oct 31, 2016

NEFFx said:
I use a pump to stir it about once a day (timer). I feel the frequency doesn't need to be as high since the volume is large compared to a regular kalk reactor, it also alows me to reduce the likelihood of suspended particles getting into the system. As much as I'd like to add new, premixed kalk to the system, its just not feasible with my schedule. My understanding is that the kalk will reach saturation, so it is not possible to overdose? What are your feelings on this. My tank uses about 8g a week.

That stirring sounds fine.

It is possible to overdose if you tank does not consume all the alk delivered by saturated. Saturated limewater delivered at 1.25% of the total water volume daily boosts alk by about 0.5 meq/L (1.4 dKH).

One issue with such a system is your use of the DI will be inefficient due to TDS creep between every run of RO/DI water. That will use up your DI resin somewhat faster.