Yes I’ve got a sump with skimmer and then it flows into a sponge with a sort of waterfall affect so I couldn’t imagine the 02 being low. What about all this being a weird coincidence? The 3 fish were new additions and then the firefish was 1.5 years old, sake with the barnacle blenny and I know they aren’t long lived fish. If another long term additions dies then yes I will take action
Yes, there are certainly coincidental fish losses - a group of fish die for different reasons in a short time span, and it can become confusing to see if the losses were related or not.
In this case though, the adding of new fish and the rapid breathing seen leads me to think a disease issue, most likely velvet (Amyloodinium). Could be flukes as well.....
Jay