Dialing in Light Intensity

reefer1 · Jul 11, 2017

Hi Dana and Other Experts,
I've gradually increased the intensity of my LED lights over the past 2-3 months and noticed a few things: a) colors have generally improved and b) polyps on SPS are more extended.
Lately, though I noticed that the alkalinity consumption has dropped a little. So, I was thinking I may have passed the optimum intensity level. (I have a 320W Maxspect razor running 60% whites and 100% blues plus two T5 blue plus bulbs for six hours/day. It's only 4-5 inches off the water surface and my tank is 18 inches deep. There is lots of flow in tank.)

Does it make sense to adjust light intensity for peak alkalinity consumption?
Are there other ways to optimize light intensity based on some other measured response?
Any other thoughts

Thanks!

glb · Jul 11, 2017

I don't know the relationship between light/alk/coral growth but it's an interesting question. Hopefully someone will chime in.

saltyfilmfolks · Jul 11, 2017

reefer1 said:
Lately, though I noticed that the alkalinity consumption has dropped a little.

First, by how much? Within the amount of possible test error?

saltyfilmfolks · Jul 11, 2017

reefer1 said:
Does it make sense to adjust light intensity for peak alkalini

Imo no. Clearly something is working well there, why change it? It would make sense to me, that it would be the other way around, adjust alk to meet higher demand.

glb · Jul 11, 2017

I second this. Don't mess with things if everything is stable.

reefer1 · Jul 11, 2017

Sorry for the confusion.
The alkalinity consumption has gone down a little. That is, my alkalinity has increased because the corals are consuming less...

saltyfilmfolks · Jul 11, 2017

reefer1 said:
Sorry for the confusion.
The alkalinity consumption has gone down a little. That is, my alkalinity has increased because the corals are consuming less...

I'll go back to this question

saltyfilmfolks said:
First, by how much? Within the amount of possible test error?

saltyfilmfolks · Jul 11, 2017

A good read. Actual experts there https://www.reef2reef.com/threads/chase-the-alk.312824/

reefer1 · Jul 11, 2017

Hi Saltyfilmfolks,
I test alkalinity every day to two days. I try to test around 3pm.
Results have drifted up while I pushed the intensity a little higher.
A month ago I measured consistently (over several days using Salifert) at 8.3dKH
Now I measure consistently (over several days using the same exact approach) at 8.6-8.75dKH
If anything growing corals should deplete the alkalinity a little faster (meaning it should be lower not higher).
So, it appears to indicate the higher light intensity has led to less alkalinity absorption.
(By the way, nothing else in the tank has changed. It is very stable. Big 3 dosed with automatic doser 24x/day.)

Does it make sense to adjust light intensity for peak alkalinity consumption?
I am thinking about lowering my light intensity to try to increase the alkalinity absorption back to where it was a month ago
Are there other ways to optimize light intensity based on some other measured response

Any other experts have any thoughts?

saltyfilmfolks · Jul 11, 2017

Yea, I'm not sure a .3 or .4 variation would be a concern.

mcarroll · Jul 12, 2017

First, +1 to everything Salty said.

Now, this...

reefer1 said:
Lately, though I noticed that the alkalinity consumption has dropped a little. So, I was thinking I may have passed the optimum intensity level.

There's an assumption that peak consumption is "good". IMO the evidence is that being under the peak is "better".

reefer1 said:
Results have drifted up while I pushed the intensity a little higher.

Something else to consider is that you're causing the corals additional photo stress so they're having to adapt....so maybe be they have. That could be related to what's happening. Alk consumption could actually be returning to normal (even a new normal) because corals have adapted to the new "too much light".

Definitely don't fix what isn't broke.

Nano sapiens · Jul 12, 2017

reefer1 said:
Does it make sense to adjust light intensity for peak alkalinity consumption?

Are there other ways to optimize light intensity based on some other measured response?

Any other thoughts

Thanks!

Good questions and not all that easy to answer definitively. Dana's the expert, but here's my 2 cents:

1. Adjusting light intensity for peak alkalinity consumption may not be a good idea long term. I have pushed corals to what was likely photosaturation (or even beyond), and while it was successful for a month or two, it took it's toll a few months after when I lost a few nice specimens (kicks self with foot...). I run my small reef tank about 10% shy of peak alkalinity consumption for this reason and also I don't need corals growing out the top every few months

2. As far as measured response goes, if your corals have nicely saturated colors (assuming you aren't running ULNS) and fine fluorescence under blue light (especially), then it's all good.

3. I like to use a relatively short 'peak' lighting period of 3 to 4 hours (as long as intensity is somewhere in the neighborhood of the saturation point for this time period, this is enough time for near-peak coloration to occur). Less stress on the coral, saves electricity and I find it helps in the control of undesireable algae growth.

The difficulty for us hobbyists is in knowing what the saturation point for a specific coral actually is, so it is best to stay a bit lower on lighting and err on the side of caution, IMO.

Ralph.

Dana Riddle · Jul 12, 2017

An interesting question, and I'll follow this thread closely - good to hear others' opinions. If I keep my mouth shut and ears open, I just might learn something

. This sort of 'issue' is difficult to diagnose from afar, but, at this point, I don't see a reason for real concern. If we were sure the alkalinity consumption is due to increased light I would suggest reducing light intensity and monitoring alk to see if it increases. It would be great to see some PAR numbers before and after.