corys rubbing against gravel

[Corydoras4Ever]

I have noticed this before, but sometimes one of my corys quickly rubs itself against the gravel. It is a very quick, swift movement in which it throws itself on its side and then back up again.

At first, I thought that it might be caused by high levels of nitrate, but regular checking seems to dismiss that notion. My water levels are fine, unless it is something that I am not testing for?

I check for amonia, nitrite, nitrate, pH, gH.

I have seen it in the past with my corys too and it never lead to their death or anything bad like that. I still wonder why they do it. Seems like an itch to me and I don't want their slimey coat to deteriorate.

 

[TankGirl]

This sounds like classic "flashing" that is a response to external parasites. Can you see anything on the fish, stuck to the scales? I would quarrantine the fish, but I am the nervous nellie type, LOL!

 

[Corydoras4Ever]

Don't see anything

I don't see anything stuck to their bodies or sides or anywhere.

 

[TankGirl]

That is good, but many parasites are not visible so it could still be what it is, as that is one of the leading causes of flashing. Another thing that can cause flashing is a drastic water change that woudl cause a pH swing.

If the flashing continues I would suggest treating for parasites, which can often be accomplished with high temps (86F) and salt, except cory's don't care for salt so skip that in this case.