All coral are retracting

[mtx]

Good day,

It has been two day now that my coral are not very happy. It happen two nights ago when I notice that all my coral have retracted. I decided to leave it and see how things will go. Well the same night, I took a look at the tank and it was not getting better. My thoughts was to wait until the morning and see how things goes. Then comes the morning when I checked again and things did not improve. I decided to leave it for the day and once I come back, I'll do a water change.

Coral:
Frogspawn, hammer head, torch - all retracted
Acan and candy coral - also retracted
one LPS - lost all it color and was truning white

So prior of doing a water change, I decide to test my parameters. I did not bother testing nitrate as I was going to do a water change. Results was 0 Amonia, 0 Nitrite and 7.8/8.0 for PH and temperature was 78. (seems all normal right?) So I went ahead and did my water change.

After the water change, I notice that I lost 2 of my sexy shrimp and the only left was not doing to well. Corals seems to have somehow start 'bubbling' again. However after 2-3 hours, things came back to how it was. Checked again this morning ans same thing.

What should I do next?

My setup:

6 gallon
7-8 lbs of LR
5 lbs of LS
12' 50/50 LED Reefbrite
2 3w LED and mini compact coralife bulb

Thanks

[JetJumper]

6Gallons is one of those things if something dies.. then the entire tank is effected really quick.  I would suggest water changes 50% over the course of the next few days.. Something seems like its in there causing a spike in something.

[Severum]

Was the water change water the same temp and salinity of your tank? If not it might explain why you lost your shrimp.

I second the notion of a small water volume being effected. I'd recommended daily/larger water changes until things start to improve.

[mtx]

Thank you folks. I'll keep doing daily water change and hopefully it will come back to normal soon. I always make sure that the salinity is the same in the tank prior of dumping the new water in. As for temp., not always the same as it is at room temp.. Since it is such a small amount of water (usually 10-15% weekly water change), I was doing it without heating the water up to the 78 degree as per the tank temperature and had no problem.

It was tough seing two of my dead shrimp. It was my favorite species in the tank.  :'(Hopefully the 3rd one will survive.

[Severum]

Maybe it was a molt... you never know.

[mtx]

Nope, it was not a molt. I came back home yesterday and was hoping for the best... last sexy shrimp was on the sand bed along with my shrunk shrimp and 1 turbo snail. 

I took everything out of the tank and check if there was any other dead thing. Did a good cleanup of the gear using RO water. (scrubbing the thermometer, AC 30, change new filter floss and clean glass of the tank) Put everything back, mix some new water/salt and did a 40% water change.

I check this morning and seems like thing might slowly get back to normal except for one frogspawn. We will see how things goes tonight and I'll do an other test of my water parameters prior of doing an other small water change.

[lost_at_sea]

keep in mind that Temperature has a direct relationship with Salinity.

ie the water's salinity at room temperature is not the same as when the same water is heated up to 78'F.

in a tank that small even the slightest change in temp (therefore salinity) or even pH could easily shock the inhabitants.

how accurately are you measuring salinity and i'd look to double check your pH too, if your tank is 7.8-8 i bet your new water is prob 8.1-8.2.