Today I came home from work to find my Orange Diamond Watchman Goby swimming in circles. I noticed that his head was red under his skin (where his brain would be and you could see a vein) so I'm not sure what happened. He could only make right turns. Well hours of him swimming and going in circles, he finally died. Has anyone seen this before? I am very sad as he was one of the first fish I got for my tank! Any help would be appreciated.
Oh, I did a test because it freaked me out and my parameters are:
Last water change: Sunday (RO
water with salt mixed for 24 hours)
Water parameters were same as above before the water change.
I have a 75 gallon with live rock and changed out 15 gallons.
Nothing new has been introduced in the tank.