Alkalinity in the reef aquaria

[aaron23]

Howdy Randy,
It has been a while glad to see you're here!

Question: (Very Generally) How much fluctuation of alkalinity can occur before you see STN or RTN in SPS corals? Again I say generally because we all know different corals can withstand more or less fluctuation.

thank you!
A

 

[Randy Holmes-Farley Verified Community Expert]

I don't really know the answer and I've not done any experimenting myself in this area. So any comments are based on what I see from other people and what seems to make sense.

I think the answer may depend on the nutrient levels, with ULNS SPS tanks being a lot more sensitive to getting burnt tips than tanks with higher nutrients seem to be. One hypothesis may be that at higher alk levels (which never happens in the ocean), the skeleton grows faster than the tissue, making it thin and susceptible to damage (such as from light) at the growing tips.

At higher nutrient levels, higher alk does not seem to be a problem and corals may grow faster.

So the question then becomes how much variation is OK. I think variation of less than 0.5 dKH may not usually be a problem, even in a ULNS, although in ULNS that may be getting close to the limit.

The answer may also depend on what you mean by variation. Alk varying from 7 to 8.5 dKH EVERY day may be OK (like with once a day alk dosing) while being at 8.5 dKH for a long time then jumping to 7 dKH for many days (or the other way around) may not.

In general, for a ULNS tank, I'd keep alk at 7-8 dKH and try to keep variations less than 0.5 dKH.

In a nonULNS I'd let the alk go higher if I wanted faster growth, and might allow a bit more daily variation.

I readers have experiences that support or dispute these values, please chime in with them.

 

[Myka]

I readers have experiences that support or dispute these values, please chime in with them.

I agree 100%. I have had (all) these experiences you describe.

 

[FranklinDattein]

+1.

More than .5dKH/day causes SPS burnt tips on my ULNS with alk at 7.8dKH and amino acids supplementation.

Also, this same system copped with a few spikes of 11-14dKH, for periods of 3-4 days. Burnt tips quickly recovered soon after Alk stabilised.

 

[aaron23]

I was fascinated to hear that ULN systems require such precise parameters. I'd only assume that these systems are very very well established?

I just started my 40 gal aquarium after my previous crashed from a big snowstorm. I had a calcium reactor on it then and I just started using 2part for this system with dosing pump. I'm currently testing alk daily and dosing 3ml of 2 part. Part of me is worried that as I increase the amount of SPS I may not add enough and swing the alk!

Follow up question:
If say a relatively new system ~1 month, began heavily stocking frags. Will there be a moment where I will need to make an immediate correction in the 2 part dosing (aside from daily dosing) or will adjusting the daily dosing incrementally be sufficient to not swing the alk and to keep it stable?

Thank you so very much randy, myka, and fsamir for entertaining my crazy question.

 

[FranklinDattein]

Short answer: no.

You need a tank fully stocked with hard corals and failure in supplementation, to cause a Alk swing, due to skeleton growth.

Addition of Frags or even large colonies will slowly increase the consumption. You just have to keep a test schedule and adapt as it increases.

 

[biom]

I would say aside of alkalinity part, that starting heavy stocking with SPS in just one month old system is not good idea at all.

 

[Randy Holmes-Farley Verified Community Expert]

I was fascinated to hear that ULN systems require such precise parameters. I'd only assume that these systems are very very well established?

.

It is a drawback to them, IMO.

In any new system with corals, I think the demand will slowly ramp up as they become established and grow faster.

 

[aaron23]

Thank you randy and all for the great advice!