Vicious Pearl Danios

[Cardinal]

I have just introduced 10 Cardinal Tetras to a 125 litre tank containing 5 Pearl Danios and 3 Cory Catfish, the Danios will not leave the tetras alone at all, they keep chasing and pecking at them. At the moment I have just scooped the danios into a floating bowl but I'm not sure whether they will be vicious again if I reintroduce them! What should I do as I like the pearl danios and don't really want to get rid of them??? Help!

 

[WILDER]

I would add some more danio's might be as the cardinals are in a bigger shoal, good luck.

 

[sinistral]

Probably territoriality...the danios have been in the tank longer (I presume) and feel it is theirs. If your tank is heavily planted or otherwise decorated, you could try turning off the lights, adding the tetras and waiting. In a 125L (33 USG) tank, there's enough room for both species. The cardinals will find hiding places until the dust has settled. The danios will probably calm down by the next day or so as they'll be used to the intruders by then.

 

[Tokis-Phoenix]

It might also be worth stocking up on some extra planting to make more hiding places for the fish so they feel more secure