Question / need advice

Hey guys n gals,*
*Just looking for a outside guess or view I'm currently out of town working be home late tomorrow*
But I got a call from my fiancé that there was algae on a few tips of my sps and one monti cap started turning white and my purple haze Monti is also turning white from my research last night it sound like my alk dropped and caused this ?*
Does this sound right to you?*
What else could cause this to happen in 5 days since I left ?*

Tank info ,*
50 gal 20 gal sump*
Tests before I left were*
Alk 11*
No3 0*
No4 0*
Cal 420*
Ph 8.2*
RO water from the start and also in my last tank were most of this was moved from*

I did a 10 gal water change a day before I left*
I don't dose*
I do run GFO in a reactor*

I'm kinda lost right now*
Thank for any info 3Reefers*

 

Is it possible to get a picture of the algae and the monti? How is the temp of your tank and the light schedule?

 

I'll try to get one up from her
Temp is 76-77 steady
Lights are on 9am to 7pm first two ATI purple And ATI blue
10 am to 8 pm ATI blue plus and another ATI blue

 

This is the best pic she could get

 

Bump

 

I would retest for nitrates and phosphates and PH, do you have any other algae?

 

Hey Silor,

That is a huge bummer. So this is only affecting montipora?

Just a wild guess but you have alk of 11 and running GFO, I too suspect that the answer lies somewhere in there. That for some reason you had a swing either way, it may have been aggravated by the water change to a small extent, did you also add new GFO at the time of the water change?

What salt are you using?

Are all power heads and pumps working, any new equipment?

I do not use GFO of present but I have heard that it can cause rapid drops in alk and pH.

 

I haven't noticed a rapid drop in alk and pH using GFO. But I also dose multiple times a day. I does sound like a rapid change in parameters. When is the last time you change filters in the RO unit? Is it just RO or RO/DI?

 

She did manage to test for nitrates and they were 0
She said she didn't understand the phosphate test I'm sure there 0 but that's guess at this point also I don't have a Hanna
I have no other algae in the tank just light green on the new rocks that's been turning pink shortly there after :/

 

At this point she says its only affecting one Acro in the pic and that one monti also in the pic but i suspect there's more being bothered at this point
I added the new gfo about a week before on a previous water change
I'm using corallife salt brand mix to 1.025
She said all pumps are 100% working and I have added no new equipment