Does fish flashing always indicate disease?

I've been well aware of the symptom of flashing or rubbing on decor as a good indicator of parasite infestation and recently read that the flashing is a distress sign for many issues including high ammonia levels. I read today that flashing occurs after water changes due to the adjustment to the water hardness. Is that true? I can't find another site to back it up so I figured I'd ask some experts

 

that all sounds right to me although I'm no expert. now flashing can also just be because they have a itch, but a lot of flashing usually means more. other causes could be nitrite, nitrate, and ick. my yoyos have ick and go crazy rubbing at times.

 

Yeah like most fish keepers I've experienced ich but I didn't realize there were other less incriminating causes as well

 

The occaisional flash with no other visible signs can be nothing at all. like mentioned above it could just be an itch. But if it is being done frequently then there is a good chance that there is something more. Most likely cause is ich. Even if there are no visible signs of it on the fish it would be starting in the gills. Another cause could be gill flukes, a parasite that lives in the fishes gills that is not readily seen on the fish. Water parameters are also an option. What are your ammonia, nitrite and nitrate readings? And how big of a water change are you doing? If it is 10-20% then that should not be a big enough change in water hardness for the fish to flash

 

It could be nothing if it's every once and a while, but honestly if it's happening enough for you to be worried enough to post and ask for help (which is good!), it probably is an indication of something more going on. I would definitely check all the vital stats (pH, Ammonia, etc) to see if this is the cause, but more often than not, its Ich -which every aquarist has to deal with at some point or another. There are several solutions to Ich starting with salt and ending with medications that turn the glue at the corners of the tank blue/green. Try not to start at the end .
Good luck!