Question
I recently bought three fantail goldfish (two ranchu and one oranda). My oranda is usually very active, eats when food is put in the tank and interacts well with the other two. However, a few times I have come to find the oranda motionless in one of the plants in the tank. It typically lies between one of the arms of the plant and the tank wall. Is there something wrong with the fish? I have checked closely and it doesn't appear to have any diseases.

Answer
Fancy goldfish like orandas often will just lay around.  At the same time, such behavior can indicate problems such as water quality issues or illness.  It's really hard to tell those apart.  If the fish is eating well, and active during feeding, swimming normally, I wouldn't worry too much.  What is the tank temperature?  How big is the tank?  Whenever you suspect a problem, be sure to check the water quality - pH, hardness, ammonia and nitrite.  I suggest weekly 30-40% water changes with added dechlorinator and a tablespoon of aquarium salt per 5 gallons.

Good luck!