Help! GiAnt danio swimming upsidedown

[Pleco96]

Danny, my giant danio, has recently been bullying some of my smaller fish in my 30g tank. I decided to relocate him to a slightly smaller tank that I had previously used to raise some guppy babies. When I first put him in, he seemed really calm which I thought was weird because usually he is so energetic. He was even slower this morning and is not eating(usually he eats more than his fair share and steals the other fish's food). Currently he is swimming upside down really slowly and keeps trying to wedge himself into small places( like behind the thermometer and under plants). I don't know what is wrong with him and i'm really scared. I am only an amature aquarist so i don't know too much about tanks. My parents are the main caretakers. I feed him omega one flakes and i keep the water at 75 degrees. Please help!

 

[Pleco96]

Never mind. He just died.

 

[Delapool]

Sorry for the loss.

It sounds like a shock from changing water conditions. Did you take any test readings at all? Normally I transfer fish ok so looking to see if there was anything for future.

 

[anteatergoanna]

Oh dear, I am so sorry for the loss of you beloved fish. It's hard to know what to do for the best sometimes, and moving your fish was for the right reasons.