Alk/Ca demand reduced, why?

[zibba]

Let me set the stage: I have a relatively new tank that's been running for nearly 8 months and has had corals for 6 month. I dose 2-part exclusively for cal, alk and mg demands. I typically test my parameters (at a minimum) weekly. At one point, I was dosing about 80 mL of both calcium and alk every day and I started noticing that my levels were creeping up a little higher than I normally run. [alk = 7.5-8.5, ca =420ish and mg = 1350].

Lately, (within the past month) I've only had to add around 10-30 mL per day. And yesterday I didn't even dose because my alk was at 9.5 and cal was 450. I realize those numbers are all fine but I'm wondering why the demand would go down even though I haven't removed any corals (in fact I've added more). I think growth has slowed down, while colors have improved. Just stumped and wanted to see if others could chime in with some ideas.

Thanks!

 

[evolved]

Temperature change?

 

[zibba]

Temps have stayed in the same range (78.5-79.2) with one exception, two days ago the ac went out and it crept up to 80.2 for a maybe 30 minutes or so and the chiller brought it down.

 

[evolved]

Higher temps = faster growth, so no.

I was thinking perhaps it now being summer, the chiller was keeping it cooler than it was before.

Only other things that come to mind, are changes in lighting (I know that's a no), but even down to changes in moonlighting. Corals mostly grow at night. Else, a pH change (higher or lower average, or bigger swings than before) or an available food change (either now too little or now too much).

Oh; another afterthought. The now missing clam will make your Ca usage decrease for sure (to some degree).

 

[zibba]

Good food for thought on all accounts. Didn't think about the clam using that much but it's about the same time period for when usage went down. pH has been a little more swingy now that I'm not adding as much alk, which raises my pH.

Maybe it's time for me to replace my halide bulb. Colors are improving so I havent though. hmm....

 

[zibba]

Is there any credibility to the thought that new frags will take up more initially when being added to the tank?

 

[evolved]

That's not one I've heard before nor ever made a correlation to, but maybe?

 

[evolved]

And I didn't mention this one since I know the answer, but it's not a PO4 issue (someone else might bring it up). 0.01 on a Hanna.

 

[Elliott]

you answered your own question, growth has slowed down so there is less uptake, hence less demand

 

[zibba]

you answered your own question, growth has slowed down so there is less uptake, hence less demand

Fair point. So I guess, knowing the above, any idea why my growth would have slowed down?

 

[Elliott]

difficult to know, besides light and flow, growth depends on so many factors in water quality, some are still unknown, many need optimal conditions for proper growth

IMO, after environmental conditions of light/flow/water quality are met, proper feeding greatly influences corals ability to thrive