May I know what disease is this?

[alanhoon]

is it a fungus? do I treat in the tank. with what meditation. thx

 

[pops]

all the meditation in the world not help, as for medication, water perams help, water change schedule and a better pic help, just guessing we dealing with a fungus. I would do a large water change then treat with polygaurd, its a broad spectrum but will not hurt your bio-filter. If this does not work, and you are doing water changes to keep nitrates below 20ppm I would move to methylene blue baths.