Originally Posted by AussieReef
It's not solved as mentioned they have been fine until this morning they have been in there together for months
It doesn't matter. Stress isn't instantaneous. Here is my theory as to what happened.
After serveral months one fish, probably the humu humu trigger which needs ~120 gallon tank. Sucumbed to stress and died. The death probably caused a spike in ammonia which let lose a chain reaction, killing all your live stock.
It was only a matter of time. I suggest you put a LOT more research in before you purchase ANY fish. And NEVER take the fish store's advice. They're more about making the buck than keeping the fish alive more than 80% of the time.
What may have also happened is that the anemone died and poisoned the tank. What lighting do you have on the tank?
Here are the problems you have:
1.)40L is barely enough to hold one clown GOBY let alone several large fish that require 100gallon systems.
2.) The tank being 3 months old was barely stable. I'm assuming you didn't cycle properly either.
3.) The anemone needed a MUCH larger tank. It was probably stinging the two larger fish as they swam by constantly.
4.) The anemone needed more light and more stable tank conditions.
Research is of utmost importance to reef keeping and I'm afraid you have skipped the step. I know I'm being harsh, but it's the cold hard facts. Sometimes you have to be mean to the point that either the person straightens out or the person realizes the hobby is not for them.