Causes of sudden ALK elevation

[msaba]

Hey Guys--wanted your thoughts on a sudden swing in my ALK over this past week. My tank is a 90g BB SPS tank that is 1.5 years old, usual parameters:

1.025
ALK 8.5
CA 370
MG 1350
NO3 5-10
Po4 .03-.06

Tunze ATO
ALK/CA doser 60 units both daily

My sps are doing really well, I have a heavy fish load and an oversized skimmer. The last few weeks I had been slowly increasing my nutrient load with increased fish feedings with Rods reef food as well as my usual flake/mysis/black worm regiment. I decreased my skimming to minimal as well
in order to see how I could influence my sps colors. I would say my sps are very well colored usually, but with increase in my nitrates to 25 (salifert) and Po4 to .9/1.2 (Hannah photometer) I really got an little more pop and richer colors out of my sps. I did not check my ALK for 2 days and all of a sudden it is 11! Upon closer inspection of my sps--my 'canaries in a coal mine' showed some signs of STN at the base (Hawkins, red dragon, Garf Bonsai). Anyway, my initial concern was that the elevated nitrates/Po4 was the culprit until I checked (and rechecked there ALK).

Is is possible that the elevated Po4 inhibit calcification which reduced ALK consumption? I understand that is theoretically possible, but don't know if it can happen 'suddenly' over a two day period.

This is a humbling hobby! Any thoughts on the cause of rapid rise in ALK?

Mark

[outssider]

I'd agree that something is causing less up-take by the sps and coralline algae. How's the calcium up-take. that should also be less if they are using less alk. did you fool with the lighting at all? Po4 is quite high :eek:

[bertoni]

I agree that a high phosphate level is likely to inhibit growth to some extent. That might be what's happening. The phosphate concentration in theory might have reached some level at which inhibition becomes very strong, for example. On the other hand, some water changes with a high-alkalinity batch of salt, or partially-settled salt, could cause problems, too.

[rovster]

Anytime you change something, SPS corals can shut down while they adjust to the change. The rise in nutrients in itself can cause this. If you don't modify how your adding Alk, boom....spike. It's happened to me numerous times in the past.

[msaba]

thanks guys for the responses, I had not made any water changes in the
last week, I always check the ALK of what I'm adding as well...

Royster,

I would of predicted that increasing nutrient load would have decreased ALK,
but that it based on some foggy concept in my head...

Anyone can tell me what the expected effect of increasing nutrient load on ALK would be, does it depend on the specifics of nutrient load? thanks

Mark

[swk]

It truly is amazing how small things can effect alk uptake. Temperature change, flow change, chemistry, nutrients a change in lighting, the list is never ending. Maintaining steady alk is part science and part art and intuition and is one of the great challenges in sps keeping.

I once had a channel on my t5 fixture crap out and going from only 6 bulbs to 4 dropped consumption enough to spike alk a bit, which in turn, caused an even bigger drop in uptake which I missed and caused another spike that ended up spiraling my tank into a die off. How true it is that hobby is indeed humbling!

[rovster]

thanks guys for the responses, I had not made any water changes in the
last week, I always check the ALK of what I'm adding as well...

Royster,

I would of predicted that increasing nutrient load would have decreased ALK,
but that it based on some foggy concept in my head...

Anyone can tell me what the expected effect of increasing nutrient load on ALK would be, does it depend on the specifics of nutrient load? thanks

Mark

Yes if they like the change. Still important to monitor daily whenever you change something. Only back off testing when things proven to be stable.

[bertoni]

Anyone can tell me what the expected effect of increasing nutrient load on ALK would be, does it depend on the specifics of nutrient load?
That's hard to predict. If animals are nutrient-limited, then adding more nutrients might increase the consumption of alkalinity. Otherwise, if the nutrient levels in the water rise (which might or might not happen), the consumption might drop due to poorer animal health or due to direct interference (as with phosphate). There are other possibilities, too.

[msaba]

thanks guys for all the thoughtful answers--gave me some more food for thought!!

Mark

[bertoni]

You're welcome. Good luck!