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Anyway, recently, they all have begun to pick on the small fat speckled oranda fish. They corner it in the rocks and poke it with their mouths... chase it around.. give it no rest.

Another common description: ...but the other black moore is agressive to the fantail goldfish by swimming into their fins and chasing them around the tank the black moore itself is verry young and is quite small...

This is classic breeding behavior. In the first place, people are amazed that such small fish (3 inches or more) can breed. Secondly, the fish are egglayers and the general idea is that the female deposits eggs for the males to fertilize. We don't need to get deeper than that. When the female is ready to scatter eggs, the males (and even some confused females) crowd after her. Incessantly, exactly as you described. Problem is in small facilities the eggs can be eaten as fast as they are laid so the fact that this is a breeding ritual is lost. The female can be badly battered in smaller tanks because she really cannot distance the hoard. If she appears tired or ragged she should be removed for a spell to rest. Perhaps a day or more.

Fish disease problems? Need some help? The help pages take you through the basics of the 'fish health work-up' diagnosis method and basic fish disease treatment methods.

90% of all health problems and fish deaths are caused by poor fish keeping! The key pages are essential reading for all beginners and intermediates who are serious about disease prevention.

Expanded Content by Dr. Erik Johnson, and Used with Permission; Frank Prince-Iles ©2009 All Rights Reserved