Wierd Barb Behaviour

[Jodiem]

i have 5 five banded barbs in my tank (no other fish) its 15g and one sometimes hides in the cave, (i think its a she, less coloured than others) and she is just sitting there for ages and when i lift the cave up she doesnt dart out,(at the mo she is swimming with the others)
what could it be
Thanks

 

[Tokis-Phoenix]

When a single shoaling fish isolates itself from the rest of the group in an odd place while the rest are hanging together in the open, it is often a sign the fish is not feeling well- i'm no expert on banded barbs, however this info applies to many shoaling fish like this.

Have you tested the water quality for ammonia, nitrites, nitrates and ph yet? If not, i would advise doing this with an accurate water quality test kit straight away and posting the exact results here .

Is the fish gasping/breathing heavily at all or has inflamed/sore looking gills or anus? Any white/stringy looking poop, plus does the fish look underweight or bloated at all?