Random fish death after powerhead change

[xnick87]

So I replaced my noisy powerhead with a new one last night and noticed an hour or so later that my skimmer was acting up a little. The same way it does when I change filter floss or epoxy some rock. I unplugged the skimmer late last night and plugged it back in this morning (off for 5 hours). I’ve done this before for a lot longer. Then today once my lights come on I look in my tank and find my coral beauty dead and my yellow tail damsel breathing super heavy laying on the sand. He died about 5 min after that. My tank is a 35 cube that’s been set up for a year next week. I had some soft corals(mainly shrooms and zoas) a fire shrimp and 2 clowns in there with the damsel and angel. Clowns and shrimp are acting normal and eating. I tested salinity, ph, ammonia, nitrite, alkalinity, nitrate and calcium. 1.025, 8.2, 0, 0, 7.8 dkh and 18ppm. All were within my normal range.
I’m really confused what could have happened. Both fish were in the tank for 6+ months and were healthy and getting fed a huge variety. I did a 5 gallon water a change and added a bag of carbon. I’ll probably do another w/c Tommorow as well. Not sure what else to do! Corals look happy as ever! EDIT :Also wanted to add I have a power filter on the tank that stayed running so I don’t think it was an oxygen issue. Damsel was definitely gasping for air on the sand though

 

[Jay Hemdal Verified Community Expert]

It is unlikely to have been a toxin, as the delicate invertebrates would have shown issues.
Normally, if all the fish die and the inverts are fine, it was a fish disease issue - every time. In your case though, the clowns are fine, so that doesn’t line up.
Not sure what the new power head could have done to the water - was it a name brand pump?
Jay

 

[xnick87]

It is unlikely to have been a toxin, as the delicate invertebrates would have shown issues.
Normally, if all the fish die and the inverts are fine, it was a fish disease issue - every time. In your case though, the clowns are fine, so that doesn’t line up.
Not sure what the new power head could have done to the water - was it a name brand pump?
Jay

Hydor koralia 600. I was replacing the same powerhead that had gotten noisy. Before the lights went out tonight I noticed one of my zoa colonies wasn’t as open as it normally is. They sometimes act weird but if they are closed tomorrow i guess that will confirm something in my water chemistry is to blame.