02-20-2012, 12:58 PM
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Originally Posted by TheresaMcMurrough
Flashing is the term aquarists use to describe the action of a fish that is scraping its gill area on plant leaves, wood, rock or the substrate. The fish flashes very fast against the object in an attempt to dislodge something from the gills, and usually (but not always) this will be a parasite like ich or velvet.
Sometimes it can simply be a piece of food caught in the gills; when fish eat, food passes in their mouth with water and sometimes a bit can be pushed out through the gills. I've seen this mostly with catfish like corys, when feeding frozen or live worms.
More often though it is parasitic, and if seen you should carefully observe the fish. An isolated flash is not a problem, but if it occurs frequently, or by more than one fish, it may be something.