We have had a gold fish tank in our office for 5 months..We have two fancytails and a comet...They have done fine. This morning the comet is chasing the smaller fancytail around and pushing her against the bottom and against things...Sometimes the other larger fancytail joins in...but not as much...We removed to smaller one but would like to know what this behavior is...?

Could be territorial, if both the comet and fancy are males...or, most likely, are they old enough to spawn?

Comet looking for some fancy tail? :lol:

Sorry, couldn't resist. :rolleyes:

Ha Ha That was cute... Thay are big fish not sure how old...They have been in same tank for 5 months...

It sounds like the comet is male and wants to spawn. Males, especially comets, can be pretty aggressive in trying to either lay eggs with a female or trying to eat those eggs. The little fantail that you removed may be female and the others male. Look at their gill covers. If they're in the mood, males will have little white spots all over their gill covers.

Ok it looks like the comet and the larger fancytail both have spots on thier gills..and the smaller one we took out does not....the spots are not real white but they are noticeable....We put the small one back in but they keep chasing her and pushing her into thinks...It looks like she in losing scales and looks so weak..we took her back out.. Is that normal...Should we leave her out? how long should we leave her out???

It's pretty normal for male goldfish who are in the mood to really beat up females, especially when there are more males than females. There's no telling when they might no longer be in the mood. If you could lower the water temperature, that might do it. Or, they may always want to chase her. They can harm her or even kill her if she can't get away. You may want to make arrangements for separate tanks for them. I am so glad my indoor goldfish are three boys!