Burned tips?

[reefanatik]

I got this Bonsai a couple of weeks ago and have noticed some white tips. They are definitely not new growth. Just wondering if it's too high to my lights or maybe water quality issues. I also have recently had some issues with a green slimer but I think that is because of some vermatid snails that have been releasing allot of webs on it. Not really sure.

Dkh 9.5 but turned my doser off to reduce to 8.5-9.
Calcium 390 when I first noticed tips but have raised it to 440 since
Salinity 1.026
Mag 1350
NO3 5
PO4 0
250W MH 20k radius ~10" from water, 6hrs.
4-T5s 10hrs.

 

[71xlch]

For me alk burn happens when my alk gets near 9dkh. I aim for 8.

 

[reefanatik]

For me alk burn happens when my alk gets near 9dkh. I aim for 8.

I turned my alkalinity doser off a couple days ago. It is currently at 9.2. Going to keep it off until I get to around 8-8.3.

 

[Finland]

Hard to tell from the pics, but could be alk burn. I like to keep my alk at 8. 9 or higher, I get burned tips. Another idea is something munching. I had a few mithrax crabs in my tank that decided to chew on a few sps. The corals looked very similar to your pics. couldn't figure out why tips were white and looked a little rough until I checked on the tank after lights out and caught the mithrax on top of the colony. Removed the crabs and problem solved.

 

[grevedin]

Low iodine levels could also be another potential reason.