HELP - my fish swims with no balance

[madiwan]

I have a 7 ich knife fish and 4 tetras in a 40 l tank.

the tetras are fine but my knife fish looks sick. it seems out of balance. it seems like its struggling to keep itself from floating to the top. like it has no energy at all. the head points downwards and the tail is upwards.

the tail moves but like its paralyzed from the mid to the head.

and i have no idea whats wrong with it.

the water is clean.. i do water changes every week.

if any1 can help with this.... then i can try to save the fish.

[MrDrums]

Don't know anything about knife fish, but I would start by checking your water - do u have a way of testing it now? Also a water change wouldn't hurt right now. I'm sure others will chime in soon. Hang in there.

[Red]

That tank is extremely small for a knife fish of any kind! What are your parameters

[Northernguy]

I think your knife fish is too small for thr tank and is getting stressed from it!
What kind of knife fish is it?
The smallest knife fish I know of is better than 12" when full grown.
What are your perameters as well?
Which one is yours?
http://www.aquaticcommunity.com/predatory/knife.php

[bushwhacker]

sounds like swim bladder problems, tho i have no idea how to treat it sorry, and yes the tank is way to small for any type of knife