Goldfish filters need to be on all day and night. Goldfish are the messiest fish around so do NOT keep it in a bowl. Besides filters also help provide oxygen.
They can vary in size depending on the age
It can be caused by a disease called pop-eye. It usually happens when you don't have filter. When you don't have filter and you usually clean the water out everyday, your fish can get stress and trauma from all that changing water everyday and stress and trauma causes pop-eye. Or it could be that you have two goldfishes and one of your goldfishes had been playing around with the other goldfish's eye which caused it to fall.
No, both male and female goldfish's tails are the same length. The sex of a goldfish does not determine how long a goldfish's tail will be. Usually the parents and what type of variety of goldfish the fish is will.
You will need to replace this filter every 4 months.
Carassius auratus
Goldfishes usually eat tiny bits of vegetables or meat...
It is from Spring to early Summer.
goldfish don't have legs
Unless it is a permanent filter mounted in the fuel tank change it every 75,000 miles.
if the goldfish is kept properly. it can live for up to 20 years or more. "kept properly" as in fed at a normal rate, & if enviorment is clean.
Err... as far as I know, Goldfishes DO NOT, umm... become pregnant. They lay eggs which are externally fertilised. Check your filter for eggs.
I've had many freshwater fish and room temperature seems to work. with tropical fish you may need a heater but not with goldfish.