Fish dying/dead - Heavy Breathing - Need Help

[apex82]

What a f'n day.... Just set up brand new aquarium controller and new wavemaker pumps YESTERDAY to prevent a tank crash!! Woke up this morning to 9 out of 10 fish lying on sides, breathing heavy and on their death bed.

Specs- 75g w 30gsump, refugium,euroreef skimmer

First checked temp, 78, then parameters, everything fine, no ammonia or nitrates, good alk,calc, phosp and ph. No power outage during the night and 2500 gph flow agitating surface so no issues there...

All sps doing fine, as well as hammer good, frogspawn good but pulsing xenia and kenya tree of all corals are dark grey, withered and basically dead. All inverts are fine as well, as far as I can tell. Cleaner shrimps still cruising around acting normal as all the snails and crabs.

At this point I see my coral beauty(fav. fish) go upside down and drift across the tank... bad f'n morning to say the least. I did an immediate 30 gallon water change( All I had mixed up) and got another 30 gallons mixing. During this time I ended up flooding the laundry room with about 10gallons of water from a hose missing bucket (FML).

As I write this... I moved my blue throat trigger and 1 chromis to a 10 gallon tank with fresh mixed saltwater with air pump and heater. They were dying anyways might as well try something. The rest are in main display still breathing heavy... however the clowns and lawnmower blenny seem to be doing a little better.

I need some help in diagnosing the main issue at hand...

What could affect every fish in less than 10 hours causing them to breath heavy and die with no physical damage or marks. I think this weeds out almost all parasites and bacterial infections? There is no evidence of any velvet, bubbles in gills, inflamed gills etc.


The only thing was changed the day prior was two new powerheads(very similar to the ones being replaced),reefkeeper lite with the temp probe in the tank and a top off of freshwater with a little dechlorinator added before I hit the sack.

The only scenario I can think of is some type of contamination of the water via extra chlorine in water system due to excessive rain when I did the top off or my wife was cleaning bathrooms with Tilex a few rooms away and it drifted into tank via air...? I am lost...

At this point coral beauty and 1 chromis are dead. Ones that are breathing heavy and most likely wont make it:
Flame Hawk
Blue throat trigger
Butterflyfish(forgot name)
Ignitus Anthias
2 x chromis
Spotted dragonette

Sorry for the rant it has just been one of those days... What should I do...? Just do another 30g change in the morning and hope for the best?