Some SPS not doing well

[Dr. Jim]

I have the same IM 200 EXT as yours. I have 10 XR15's over it (set at "AB Program" at 80%). I'm not sure if all of those are necessary but I'm fairly confident that 3 aren't enough (unless, perhaps, you have the SPS directly under each light).
(My system is a temporary holding system while I am renting and looking for a new home where I will build a larger custom tank. This is why all my corals are on eggcrate for now ).

 

[kratosxxl]

I have the same IM 200 EXT as yours. I have 10 XR15's over it (set at "AB Program" at 80%). I'm not sure if all of those are necessary but I'm fairly confident that 3 aren't enough (unless, perhaps, you have the SPS directly under each light).
(My system is a temporary holding system while I am renting and looking for a new home where I will build a larger custom tank. This is why all my corals are on eggcrate for now ).

yeah i actually have Island in the middle right under leds.:)

 

[ReneReef]

I just dont think now its the rigfht time to bump up the par right ? i can get 600 on that top rock and 250 on the sand , but considering all things going would increasing par hurt even more ?

PAR numbers are hardly reliable. Just rough ball park figures. You might be getting these numbers directly under the light. But your lights simply cannot be giving the proper intensity throughout your tank. Just waaaayyyyy too little.

At the moment, the lack of light is killing your acros. Or at least greatly contributing to their death.
Doing nothing about your lights, you might as well toss them in the bin right now.

 

[mcarroll]

I just dont think now its the rigfht time to bump up the par right ? i can get 600 on that top rock and 250 on the sand , but considering all things going would increasing par hurt even more ?

This is a pretty typical photosynthetic scenario, even for many acro species:

from: https://orphek.com/the-myth-of-corals-requiring-unlimited-amounts-of-light/

This is a very complimentary piece...note Table 1 at the very bottom of the article:
https://reefs.com/magazine/how-much...allow-water-invertebrates-light-requirements/

There really aren't that many corals that "require" (ie their saturation point) very strong light. The ones that have a saturation point that fits a higher range, it's still more true that they tolerate it than they need it. Also note the final two pics which have their Figure numbering off by two in the text for some reason.

If your current PAR levels are at least satisfying the corals compensation points (see Table 1) then it's not doing them any harm. IMO use whatever acclimation plan you had to bring the lights up to their final level....but don't systemically put that off.

 

[kratosxxl]

Folks,

My nitrates dropped down to 2.5, and my LPS corals weren't looking great. I decided to dose MicroBacter Nitrate to bring them up, which bumped my levels to 7.9 over the course of three days. Now, the LPS look significantly better, and the SPS STN has pretty much stopped (or at least isn't progressing anymore). Plus, that strong algae smell I had is completely gone!
Now I remember that the main change I made recently was actually bumping my kalk dosing from 600 mL to 720 mL overnight because I was chasing pH. 720 mL still isn't all that much for a 200-gallon system, right?

 

[Dr. Jim]

Now I remember that the main change I made recently was actually bumping my kalk dosing from 600 mL to 720 mL overnight because I was chasing pH. 720 mL still isn't all that much for a 200-gallon system, right?

With my tank, (which is the same as yours), I have my kalk reactor in series with my ATO water line running to a float valve in the sump. I'm not sure how much water evaporates daily but I'd guess at least a gallon. So, I'm probably adding 3500-4000 ml per day. As long as your alk doesn't rise too high you can add as much as you can. I also need a Ca reactor after maxing out the kalk additions. The disadvantage of the way I add kalk is that different amounts are added every day because evaporation varies. I'm constantly tweaking my Ca reactor because of this. I may go back to a uniform kalk dosing schedule like I previously used. I've only been using the current setup for a couple of months. I'm maximizing my kalk additions but probably creating less stable alkalinity because of evaporation variations resulting in different amounts of kalk daily along with constant Ca reactor additions.