Flashing and rubbing
Repeated scraping against rocks or substrate can signal skin or gill irritation. Check water first. Parasites are one possibility, but identifying them often requires microscopic examination; rubbing alone does not tell you which medicine to use.
Jumping out of the water
Check sudden water changes, low oxygen and aggression. Use a secure ventilated cover with protected cable openings. A lid prevents escape but does not resolve the trigger, so investigate the conditions below it.
Chasing and aggression
Spawning pursuit, feeding competition and crowding can all cause chasing. Observe whether the pursued fish can rest and eat. Separate fish into appropriate housing if one is injured or persistently harassed; do not rely on extra food to stop the behaviour.
When to get professional help
Seek urgent help for severe breathing difficulty, bleeding, raised scales or inability to stay upright. Record exact water results and recent changes. A separate hospital aquarium must also be adequately filtered and aerated; an uncycled bowl can make the problem worse.
Frequently asked question
Should I medicate before testing the water?
Check water and oxygen promptly. Treatment should follow the likely cause; avoid mixing remedies without qualified guidance.
Sources and further reading
General husbandry and health references. Individual fish and local conditions vary.