Day after day, gigantic alien faces peer into your home, knock at your windows, and thrust humongous hands into your living room. Ironically, those goldfish and spotted sunfish you bought last month to help you lower your blood pressure are in need of some R and R themselves. That's because fish get stressed too. And stress can make fish sick, just like it does humans, says Howard Krum, head of veterinary services at the New England Aquarium in Boston. Stressed-out fish are more susceptible to disease and take longer to heal.
Stress also makes breeding difficult for fish and even shortens their lives.
If they're gilling more rapidly than usual, that's probably a sign of stress. To keep things calm in waterworld, consider the following. Well, there are bullies in the fish world too, and they can traumatize their more timid targets by poking, chasing, and taunting them into submission. To prevent turf wars in your tank, stick with species that get along. Ask the owner of your local pet store for guidance.