Barra

hi, um my barra has got this white patch on its fin
any ideas on wat it would be

nitrate:40
nitrite:less than 0.5
water hardness:120
total alkalinity:80
ph:6.8

this is a photo of it
cheers

How many gallons or lites is the tank.
How many fish and which type.
How long has the tank been set up.

Immediate water change and increase aeration with having a nitrite reading.
Do you have an ammonia reading.

Does the white patch look fluffy like cotton wool as it hard to tell in the pic.
Or strands of cotton.

it a 3 foot tank so i think it about 40gallons
i havent got a ammonia reading
no other fish i had a couple of brisle nose catties in there but he ate them
the tank has been set up for about 3 months
ive been doing water changes every week at about 25 percent
ive added about 1kg of salt to keep his stress leves down
the white mark isnt cotton like. it look like his pectoral fin is changing color to a milky white.
when i first noticed it i thought it might have been a birth mark. i watched it for a couple of days and noticed it was getting bigger. he keeps flicking his body on the ground i asked my LFS about it all and they had know idea they asked me tho bring him in so that they can have a look at him but i want to try avoid that since his about 300mm long and he stresses pretty easerly.

What type of test kit are you using.

Take a sample of your water and ask them to write the readings down for you.

Flicking and rubbing can also be caused by bad water quality.

Is this type of fish big waste producers as your filter might not be coping with the fish.
Also the fish sounds big for a 40 gallon.

Milky fins can be bad water quality, parasites, ph shock, bacterial finrot.

the test kit its a mardel 5 in one test kit, basicaly there little test strips you stick in the water and then pull them out and have a look at what color the little icons have changed to. um i dont know about alot of waste but there defenatly huge. he swims around the tank fine so i think the tank size is ok for the moment until he out grows it. i think it might be fin fin rot when i brought him about 2 week ago the fish store had him locked up in a 1.5 ft tank so he could bearly move let alone turn around his tail fin was showing good signs of fin rot. ive been treating it with pimafix & melafix.

Ok.

I would buy liquid test kits as there far more accurate.