Flashing

[ABee]

So, you've got a cycled aquarium. Good filter, good heater, not overstocked or anything crazy, all your fish are friendly towards each other... Then you notice one fish flashing - and only once! What should your course of action be? What do you do at the first signs of flashing?

 

[anibis]

Just keep watching. One flash doesn't necessarily mean anything is wrong. If the flashing gets more frequent, or spreads to other fish there is something wrong.