Blacknose Dace Aggression

I have a 20H (24"x12"x16") with a stock of 2 yellow perch (both 2"), 5 Johhny darters (2"-2.5"), and 5 blacknose dace (four are 1.25" and one is 2"). Believe it or not the 2" dace is actually bullying everything in the tank including the perch which I find ironic since the perch would eat them like candy when they get bigger. I've never even heard of dace attacking other fish, especially benthic rhinichthys dace so I'm not sure whether I should ignore it considering Rhinichthys species can't do much as far as nipping with their small down turned mouth or separate the aggressive one from the others.

Down to 4 Blacknose, the largest one jumped out of a 1" crack. I think I've figured it out though. If you keep them in large groups with all fish being equal size (within 0.25" of each other) they tend to just constantly harass each other instead of the other fish. They're just hyperactive fish apparantly . They don't bother the darters as much but occasionally they'll still nip at them. I love these four I have but I don't want to put them in the riffle tank I'm setting up I originally planned for them to go in because if they touch my Greenside darters they're going to wind up cat food . I'm thinking I might put them in their own small tank and make a little aquascape around them.

PUHUCBLMX2 said:

are they actually damaging your other fish or just chasing them a little bit? what is the "stress level" of the other fish as far as you can tell?

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I forgot about this thread, lol. All of these fish are pretty much gone at this point. The dace all got ich a while after this thread so sadly they all died. And all the perch had died of swim bladder problems. I'm down to some Johnny darters and gambusia in this tank as of now with no aggression issues. Next time I do Rhinichthys sps. I'll do them in a species tank.