not quite sure. my 10" gold severum broke out with what i thought was a standard bact infection about 2 months ago. i treated for bacteria with salt and melefix but it did not work so i used tetracycline with success...i thought. i added a new 5" green severum and now he's got it. looks like protazoan velvet but idk, never had this problem before. just big yellowish knots all over him