pacing

So quick question on this, I had dinos BAD and my clowns got sick, took them out to bring to my lfs, while they were gone, I rearranged rocks to give more swimming room (90 gallon tank) no other fish except neon goby. I got the dinos pushed back My lfs cared for them and they sat in a qt tank...

It all started when I added a midas a few months ago and ever since then any new fish I add to the tank will always die after a week or two however it does not affect inverts. The symptoms displayed are a reduction in appetite but still eating and gently pacing the glass. At the end the fish...