Sick Cherry Barb

[Realtree]

One of my cherry barbs keeps laying on the bottom of the tank and looks dead. But when you attempt to net it it swims off and hides. It has been like this for days now but does not seem under nourished. What do you think and any advice appreciated .

 

[WILDER]

Size of tank in gallons or litres.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.
What do you feed the fish.

Does the fish look bloated.
Can the fish maintain balance in the water.
Does the fish tilt to oneside when resting.
Does the fish look pale or darker in colour.
Is the fish acting sluggish and lethagic.
Any red sores or red streaking on the fish body.
What does it look like when the fish goes to the toilet.
Does the fish lay on it's back or turn upside down.