Lopsided Zebra Danio

[overawy]

Tank size: 125L
pH: 7.4
ammonia: 0ppm
nitrite: 0ppm
nitrate: 20ppm
tank temp: 24C

Fish Symptoms (include full description including lesion, color, location, fish behavior):
Just noticed today that my Zebra Danio is leaning to one side, it is still eating and chasing the other danios. It seems like it is not moving its one fin.
I hadn't noticed any direct fighting so just wondered if you guys think it could be something else?

Volume and Frequency of water changes: 25% Once A Week

Chemical Additives or Media in your tank: No Chemicals, U3 Media And Filter

Tank inhabitants: 5 Zebra Danios (I believe 2 males + 3 females) and 3 Neon Tetras

Recent additions to your tank (living or decoration): None

Exposure to chemicals: No

Here is a youtube link to show what the danio is like http/www.youtube.com/watch?v=3bjZE5aqL4Y

Any help appreciated guys

 

[WILDER]

He dosn't look bloated.
What do you feed your fish.
What does it look like when the fish goes to the toilet.

 

[overawy]

They get fed on Nutrafin Max, once a day, and usually get fed frozen bloodworms once a week

They only get fed once a day

Haven't seen it going to the toilet yet

in Swim Bladder do they always get bloated?

Cheers

 

[WILDER]

Yes fish can bloat up with swim bladder.
Causes of swim bladder are, bad water quality, unstable temp, poor diet, injury, birth defect, bacterial infection of the swim bladder, internal parasites.

Try and get some frozen daphnia.
Feed some shelled peas.
Introduce some frozen foods like brime shrimp, daphnia, and green veg into there diet.