Sudden sunburst anthia death

[authentic]

Two days ago found my Sunburst Anthea upside down in the corner of my tank. Reached in and it swam away. Next day found him stuck to the edge of my overflow. Again reached in and swam away. This morning he was a goner

Everything the tank is doing great the only thing I can think of is aggression from my Borboneus as they are both similar shapes, to the point that when I found the Sunburst I actually thought it was my borbonius. Maybe as they got bigger the tank was too small for the both of them, 140 gallons.

In hindsight I probably should have removed the Sunburst and put him in my sump the first time I found him

 

[Havens_Reef_Aquarium]

I bought a Sunburst Anthias and (2) days later, he was dead. Are these fish hard to keep? I have never had a fish die after (2) days. My tank parameters are good, little high on the nitrates (20ppm). Any advice or knowledge would be much appreciated (-:

 

[USMC 4 LIFE]

These fish generally like to perch themselves sideways, upside down and in weird positions. Mine does this all the time.

As for maintaining them, I think they're relatively easy as long as you feed multiple times a day and have non aggressive fish with it.