Fish With Buoyancy Issues

[Bristlenose]

Quick question as to what is affecting one of my Tetra's. He is having buoyancy issues and has to point up and swim in that direction in small twitchy sperts to remain on a chosen level within the water. He also twitches to his left whilst going forwards. No other signs of illness and Ammonia and Nitrite are all normal, 0.

Any idea's?

Thanks,

 

[WILDER]

Size of tank in gallons or litres.
How many fish and which type.
What's teh make of the test kit you are using.

Does he look bloated.
What do you feed your fish?
What does it look like when he goes to the toilet.
Does it look like his tail weighing him down in the water.
Does he tilt to one side.
Does he turn upside down.
is he darting around the tank, or swimming fast in circles.

Swim bladder causes.
injury, birth defect, unstable temp, unstable diet, to many dried foods, bad water quality, internal parasites, bacterial infection of the swim bladder.