Puffer turning white on one side

[mskvarenina]

I've got a puffer that I've had for about a year. Recently I noticed he started to turn white on one side by his eye. Now the whiteness is spread to his entire left side. He no longer just swims around, instead he lays on the bottom of the tank under a rock but still comes out to eat.

No other fish seem to be stressed or effected and nothing's been added to the tank since I got him over a year ago.

I Googled this and saw a few posts but nothing was definitive on what this could be.

Thoughts?

 

[microlady]

Bacterial or fungal infection?

 

[Deinonych]

Pictures would help with diagnosis if you can post them.