Fish die off

[dough]

Over the last few days, all my fish have died off.  This was before and after a large water change with the same salt.  The die off included new fish and fish that I have had for years including hardy fish such as clown fish.  Corals seem unaffected by this.  All my corals look healthy.   The peppermint shrimp are okay as well as my snails.

Over 20 years of keeping a tank this has never ever happened to me.

pH is 8.10

Salinity 1.028 which is high but not fatally high.

No sign of ich, or velvet patches. The remaining gobie in the tank has some dark spots on it.  Not changes in food that I feed etc.

Any thoughts on what I should to do to start diagnosing this?

 

[bcavalli]

Im so sorry that happened,  I cant even imagine how devastating that must be.   Did you recently add any new fish when this started happening?  My first thought is you must have added a fish that is a carrier of some type of disease which spread throughout the tank.  The only other possibility is lack of oxygen or a contaminate.  The symptoms of the fish prior to death may help as well to determine the cause.  Just trying to throw a few ideas out there.  Again, that must be horrible and devastating.

 

[lmm1967]

@dough something odd has to have happened.

Whats your Ammonia at? I know - mature tank = no Ammonia issues. But - start simple first. What are all your parameters? Anything going on inside or outside the house? Construction outside? New cleaning products? Exterminator? Anything?

Did you or someone stir up a ton of sand? Make any changes to your sump? New batch of food? Recent bacteria blooms? Any new filter media (carbon,gfo)? Just change out your RO/DI Filters?

 

[saltwaterwannabe]

Sorry to hear this.  I have heard of a large gas bubble released from a deep sand bed doing this before, just a thought.  I have never had it happen myself.

 

[dough]

The last fish added was a small tank for LiveAquaria a few weeks ago.

Don't have test kits for ammonia etc.  But again I did a 15% water change Sunday in the middle of the fish die off.

We had some painting done in the house a few weeks ago as well but not in the room with the fish tank.  It was latex paint and I have painted before with out any impact.

No new foods, change filter sock during the water change as normal.  Nothing out of the ordinary.

Thinking the tang may have introduced something into the tank, unless corals can carry parasites.

 

[bcavalli]

My money would be on the Tang.  I was thinking about it and maybe it was a cascading event.  You could have had one or two larger fish die and maybe saw an ammonia spike as Leo added might be a cause.   Do you remember any symptoms the dying fiah were exhibiting?  Just a few possible symptoms, heavy breathing, darting around, sit on the bottom of the tank?

 

[thewonderdog]

I have been keeping marine tanks since 1979 have had a major die off of fish only once. the tank a 55 had been stable for 10+ years and after the event and a few 50% water changes went back to being fine for a number of years matter of fact it was my first reef tank any way the only thing I had done different before the die off was a 15 to 20% water change using the then brand new reef crystals not blameing them but.. One of the biggest joys of this hobby is its always something new. Also one or the biggest disappointments . stick with it and good luck.
Tom