Fish swimming on it's side

[Exotic Reef.]

So yesterday I notice my blue damsil on the sand up right like a normal fish the today it was on it's side like it was dead and was also swiming like this it also had a big eye i also have 2 other fish they seem to be ok ...anything else you need to know about my set up to help me out just ask
Thanks

 

[sarahlovesfish]

maybe the water quality may not be good, or the fish has been injured by the other 2 fish. check your water parameters, and keep an eye out if you see the fish bullying that one.

 

[Exotic Reef.]

I think it may be my water qulity In my sump the green stuff it was not there when I first put the sand in and it spreader alil in the sump sand ..and I'm using Rodi water I need to look in to this more thanks