8 goldfish in a ten gallon tank?? That is WAY too many goldfish for a ten gallon tank! Goldfish need 10-20 gallons PER fish! You dont mention what type of goldfish you have. Common goldfish, comets, and shubunkins grow to be over 12 inches long (and should be in a pond!). Fancies can grow to be over ten inches long. Goldfish are extremely messy fish that need great filtration, lots of vaccumming, and lots of water changes! I hope this helps!!