Declining ALK!

[JD'sReef]

What could be the reason that I am constantly add ALK buffer? I am adding it like every other day to keep the ALK between 7 - 9 PPM. The cacium is staying right around 400 (working on getting that higher) but the alk is always fluctuating.
Thanks,
J.

 

[hotrodder]

I would like to know as well. I have to increase the output on my calcium reactor. I have the same issue.

 

[JD'sReef]

That is two of us who need advice, come on yall.
I was brainstorming about this last night. Because the tank is like 4 years old, could an old sand be causing the fluctuation?
J.

 

[brandonberry]

the breakdown of wastes by aerobic bacteria creates nitric acid which lowers alkalinity. This could be the cause, however I'm not sure how much nitric acid is produced or how greatly it should impact alkalinity. Also, this effect is supposed to be reversed when the anaerobic bacteria convert nitrate into nitrogen gas. What type of bio-filtration do you have: bioballs, sponge, live rock, dsb, etc?

 

[JD'sReef]

I have about 35/40 LBS of live rock in a 46 Gallon bow. For filtration I am using a E.T.S.S. 600 downdraft skimmer along with some angle hair for final polishing. I don't feed them that much so there is not that much waste. However, I am not the most up to par individual when you are speaking all tecky like you just were. Thanks for helping me ponder some ideas brandonberry.
P.S. - There are bioballs in the downdraft part of the skimmer. Could they be dirty and causing this issue?
Thanks
J.

 

[brandonberry]

I also use and ETSS skimmer. I don't think the bio-balls in it are the issue, however it is a good idea to clean them periodically to make the skimmer work properly. I'm thinking it may be possible that the angel hair is causing the problem. If it is due to the nitric acid from the aerobic bacteria, I would think it may also be coupled with higher nitates. Have you tested nitrates?

I also remember reading one of RHF's articles stating something to the effect that even though it appeared that calcium/alkalinity were being depleted at different rates, they actually were not. I can't remember why this was or which one was supposed to appear to be depleting faster. I don't have time to research it now, but you may want to go back and read his calcium/alkalinity articles.

 

[tgfrench]

I'm not going into all the deliberation of others. My answer would be to add more of your alk solution. My experience however humble has been that alk is used up quicker.

 

[JD'sReef]

Yeah but think about it in my perspective. If Alk and Ca work in unison, then why is alk only falling, shouldn't the CA be crashing as wel?

 

[brandonberry]

For calcification that is correct, but for nitrification, it is not. The formula for nitrification is:
NO2- + 1/2O2 --> NO3- + 2H+

Therefore, for each molecule of nitrite converted to nitrate, 2 hydrogen ions are released causing a decrease in alkalinity. This process should not affect calcium though.

 

[JD'sReef]

Alright, this has flown over my head. I am going to track it hard core and then report back.
I was tracking it but not in a proper fashion.
Thanks,
J.

 

[brandonberry]

Bottom line, you just need to test it occasionally and add more buffer to adjust for the loss.