I have a 10 gallon with 3 zebra danios, 3 cory cats, and 1 albino bristelnose pleco. Temp is 78, pH is 7.4, ammonia and nitrites are 0, nitrates are 10 ppm. Chlorine/chloramines are removed (and pH adjusted) with Wardley 3-in-1 pH 7.0 conditioner. I do weekly 35-50% water changes.
Over the past few months, I've noticed all three of the cory cats scratching themselves repeatedly on gravel and clay pots. I have noticed the pleco and one of the danios do this on just one or two occasions. Otherwise, all the fish behave normally and have no outward signs of disease (except one of the cory cats has missing barbels).
I have been maintaining a level of 1 tsp/gallon aquarium salt. I have treated the tank a couple times with Jungle Parasite Clear, but there has been no change from that. I just started treatment with CopperSafe and Maracyn.
I assumed that the scratching/flashing meant that the fish must have an external parasite, even though there are no visible signs. Could something else be bothering them?
What do you typically do when fish are flashing? Thanks.