Water Turned Milky

[Jbram]

I went on vacation a couple weeks ago and 3 day in I get a call from my friend watching the tank.  The water had become cloudy, he described it as milky.   He has had tanks for 20+ years and has never seen this.  I lost almost all of my tank.  He did a 30% water change and things cleared up.  Any idea what would have caused this?  I do not have any pictures to post.
 
The living stock is doing fine, eating well and the water tests all look good, both mine and from my trusted LFS.

 

[looking-glass]

have you tested your water - it can be the presence of ammonia that can cause this

 

[Jbram]

Yes  ammonia - 0 , Nitrate - 10mg , ph - 7 . nitrite .1.  But this is three days later.  It turned milky 3 days ago and friend did a 30% water change and it cleared up.  It is crystal clear right now.

 

[coolie]

The fish that survived, how many and which species? Which species died?

 

[Malex530]

Is your tank cycled? Was he overfeeding? How many gallons? How many fish?

 

[Jbram]

This is a 120 gallon tank.  I lost 6 angels, one BNP, breeding pair of GBR, 10 Rasboras, 8 Panda Cories. 
 
The fish that lived: 1 BNP, Rubberlip Pleco, 4 Black skirt tetras, 2 Panda Cories, 2 mystery snails
 
The tank has been going for over a year and I test water conditions regularly.  My friend has over 20 years with tanks.  I did a water change 3 days before I left, 3 days after I left he called me.  He had been there the night before and tank was clean, when he came back in the morning it was cloudy, milky and livestock was dead.  He said it looked like the fish had been dead longer than a few hours, they all looked as though they had a chemical burn and there was a while fuzz covering them.

 

[star4]

Nitrite should be 0, its sounds like the tank went through a mini cycle and the dead fish caused an ammonia spike which the wc cleared up. Ask your friend to keep testing the water and do a wc again if the nitrite rises.

 

[Jbram]

UPDATE -
 
The tank has been cycling since I posted and I have checked the water every other day.
 
I added a school of 10 harlequin rasboras last week and a school of 10 pristella tetras earlier this week.  The 5 x-ray tetras that survived had some babies, I have found 3 swimming around so far.  Yesterday I added 6 Botia Angelicus, I was browsing my LFS and a girl walked in and was going to give them to the store so I talked her into giving them to me instead, Petsmart doesn't deserve those fish. 
 
The other survivors are all looking happy and healthy.
 
Active tank and everyone is getting along great.
 
The only answer I can find to what happened to my tank is I over dosed it on the water change.