goldfish agression

Question
i have a 30 gallon tank with 2 common and 1 comet.  all three are about the same size, 3-4 inches.  i noticed one of my commons, common#1, was missing a few scales while the other common,common#2, was missing just one or two but my comet was missing none.  i also noticed my comet likes to chase and nip at common#1 the most.  they weren't like this before, but then again the weather is warming up and the water temperature has been higher than usual, its in the high 70's currently. ph level is normal. what's causing the comet to be aggressive to others?

Answer
Hi Andy,

1)The high 70's is MUCH too high for common and comet goldfish! Goldfish become very uncomfortable at temperatures of 72F and higher. Their preferred temperature is below 70F. if you have a heater, remove it, since heaters are not necessary for goldfish. if your house temperature is constantly high, in the high 70's, you may need to buy an aquarium chiller to keep goldfish.

2)Reducing aggression can be done by re-arranging any cave or rocks.  If that doesn't work, you an buy a see through aquarium divider at your local fish store to separate them, and prevent further injury.

Good Luck, and happy fishkeeping!