what else causes tip burn

[StrategicReef]

I am stumped on the recent problems.. I can't seem to stop tip burns
Acros tips are burning and getting more and more severe, affected corals have little PE, actually dying from top down. There are some acros that look unaffected mostly millipora, oregon tort, etc still growing and great PE.

The alk is around 8-9. Vodka dosing was very light but now completely stopped.
CA 500.
MG 1300
PO4 won't show up.

Water change 7% every week. Carbon change every 4 weeks and GFO bag in sump.

Montis are not doing well, caps are bleached, I received a monti frag last week and it is already showing less and less polyp this today.

I don't know what else to check? Run UV?

I am using baking soda and pool calcium. Something is tainting the water?

I have a big duncan about 5" in diameter and was wondering if that could be causing a problem in a 80g tank.

 

[battplus]

500 on the calcium is really high, also baking soda and pool calcium??? Why not use a good two part?

 

[Ding2daDong]

The only thing that sounds off to me is the pool calcium. Are you sure that is 100% safe for marine aquariums? I know a few brands have extra chemicals where people have claimed after mixing a batch of 2part that it had a grease slick on the top. I don't think UV would solve anything. I also don't think it is the large duncan colony as you are running carbon. Also 500 calcium is high.

hth

-Matthew

 

[StrategicReef]

The brand is leslies pool it was recommended to me.. I have used many gallons and almost no impurity, it looks just like turbo calcium. Now since it wasn't an official reef product I can't say for sure.

baking soda I think it is food safe.

Dosing 100ml a day.