Denitrification via bio pellets causing alk to rise?

TX_Punisher · Dec 16, 2018

I’ve battled this issue for some time now. I’ve gone from thinking it was Pukani rock I started with to even the meso flakes I added to the tank over a year ago. My alk continues to rise even with large water changes which caused me to dose muriatic to keep alk in range (8-8.5).

While poking around I saw randy posted denitrification (did not mention the means) can cause alk to rise. About 8-9 months ago I started running a bio pellet reactor. The more I thought about it and looked at things, this is the only thing I can think of causing alk to rise without dosing.

Randy, any thoughts?

Thanks

Ranjib · Dec 18, 2018

Dan_P · Dec 18, 2018

TX_Punisher said:
I’ve battled this issue for some time now. I’ve gone from thinking it was Pukani rock I started with to even the meso flakes I added to the tank over a year ago. My alk continues to rise even with large water changes which caused me to dose muriatic to keep alk in range (8-8.5).

While poking around I saw randy posted denitrification (did not mention the means) can cause alk to rise. About 8-9 months ago I started running a bio pellet reactor. The more I thought about it and looked at things, this is the only thing I can think of causing alk to rise without dosing.

Randy, any thoughts?

Thanks

Randy has pointed out that nitrification of ammonnia to nitrate followed by denitrification, i.e., nitrate to nitrogen gas, would leave alkalinity unchanged. Nitrification removes as much alkalinity as denitrification produces. In small scale experiments with calcium acetate dosing, the acetate seems to be converted to alkalinity in a 1:1 ratio, increasing the alkalinity of the system. I don’t think the pellets would do the same thing.

When I carbon dosed with calcium acetate, I did notice the alkalinity depletion in my fish only sysytem seemed to decrease more than could be explained by the alkalinity increase from calcium acetate. In addition, alkalinity consumption went from fluctuating wildly before carbon dosing to a more consistent consumption rate shortly after dosing started. I don’t think this answers your question but does support the notion that alkalinity consumption might change during carbon dosing. I plan on posting this data after a few more months of data collection.