Sudden die off

I just performed a water change yesterday went to work came home this morning and one of my clowns is dead all my corals are shrunken in and all my other fish are acting very strange two are almost skimming the surface for air but the surface is agitated decently. I found SEVERAL pods DEAD. WTH happened? I cleaned off a bunch of cyano from the sand and some of the rock work, took the rocks out scrubbed them in a bucket of tank water then rinsed them and put them back in.

Ammonia 0
Salinity 1.023
Nitrate between 20-30 ppm?
Nitrite 0

What could cause this?

 

crap........ I just thought about it.... I use amquel as my De-chlorination and it says you need to over oxygenate the water.... It's the only thing I could think of.... it has to be that.

I killed my tank with asphyxiation..... the prize of my tank anyways... And I just told the wifey via txt that her beloved fish died.... oh i feel like a monster.....

 

Whats your alkalinity at?

 

my dkh is 15 my ph is 8

ph might be a little lower then 8

 

the two mollies are swimming around as if nothing has happened but my last clown is not fairing well... he's acting very lethargic. I turned both my powerhead upward to agitate the surface like crazy.

 

Your using tap water? Could be O2 due to the amquel, or just the amquel itself, no ones knows what the byproducts from amquel do. Over time, they could accumulate and become toxic if you use it regularly. However, also could just be the water. Sometimes towns/cities will flush the system and not tell you, or rain runoff etc... and you end up with all sorts of nasty stuff in the water. Salinity and a pure water source such as RO/RI and good lighting are really the 3 most important things for a reef. If your going to skimp, skimp elsewhere...

 

hasn't rained in months, but they could have done a flush of their systems. I haven't used amquel much on this tank before i was just using novaqua but because of the slime coat thing it made my protean skimmer go nuts for days. Parents house so it's unlikely they'll give me a faucet to hijack with a Ro/di unit... As much as I'd like one. Well this is a bit of a setback. Everything was going great till that water change... I kept saying to the wifey i needed to use RO/DI and now it could have bitten me in the clown...

 

now the light is on some of the corals are bouncing back and since i moved the power heads upwards it might be helping. so i could have been the O2 it could be chemical junk from the tap water.... either way I'm gonna be getting flack for a year....

 

Also imo - don't scrub the live rock and clean them out of the tank - there is a lot of good bacteria you will kill off. This bacteria is what helps keep the system stable.
What size skimmer do you have - do you have a refugium?

 

my tank is a 46 gallon the skimmer is rated for a 65gallon, i don't have a fuge, and the rock was covered in cyano to the point it was starting to grow over the GHA.

EDIT: my clown seems to have stabilized but he looks so sad hiding in his normal spot behind the power head, he keeps looking in to the acrylic at him self like hes missing his buddy.