Lonely harlie

[Shadownova]

I have five harlequin Rasboras and one is always left behind. I am a little worried because I don't know if it is sick or something. Advice

 

[bud29]

I had a neon tetra that did that and he died after a few days.

 

[absolutangel04]

Does it act sick at all or look skinny? IME, sometimes schooling fish school better when you add a couple more fish. That's what happened with my rummy nose tetras. But, the fish might be sick too. Hard to say. Is it eating normal? Pooping normal? Colored normal? Swimming normal?
How long have you had all these fish? Has that one always been a loner, or is a recent occurrence?

 

[Shadownova]

Same color and everything I think it might be a territorial thing or something like a guard because he seems to stay in the same area