I've had both of these fish for 12 days now, they've had these spots since the day they arrived, no new ones have appeared so I assumed it was normal discoloration until someone on another post said it's not normal.
2 days ago - Sunday (11/4) I did start treatment for flukes, after my yellow tang started flashing the night before and I did a FW dip on Sunday to id the problem. So far so good, he's swimming around, no more flashing. Still seems a little stressed from time to time, it took a good 5 days for him to calm down and get used to the tank, may be too small for him at 20g, but it's only quarantine. The spot is on his tail fin, it almost looks like you could scrape it off with your fingernail...not that I would!
The much smaller Kole tang never showed signs of flukes and was so scared from the net chase of the big one, that he never got a FW dip, but he's still getting the meds anyway, so I didn't bother him after he hid behind the HOB filter for 5 or 6 hours... He's had these 2 spots on his back fins since day 1 too, but they don't look white, they almost look the same color as he is, which made me think it was discoloration.
I feed them NLS marine and sometimes frozen, and I toss in a piece of algae wafer once in a while, they seem to like that. Tank is crystal clear, last I checked everything was fine, no ammonia, normal everything. Temp is 79 to 80, good filtration, filter is for around 50g and the tank is only 20g.
Any thoughts?
2 days ago - Sunday (11/4) I did start treatment for flukes, after my yellow tang started flashing the night before and I did a FW dip on Sunday to id the problem. So far so good, he's swimming around, no more flashing. Still seems a little stressed from time to time, it took a good 5 days for him to calm down and get used to the tank, may be too small for him at 20g, but it's only quarantine. The spot is on his tail fin, it almost looks like you could scrape it off with your fingernail...not that I would!
The much smaller Kole tang never showed signs of flukes and was so scared from the net chase of the big one, that he never got a FW dip, but he's still getting the meds anyway, so I didn't bother him after he hid behind the HOB filter for 5 or 6 hours... He's had these 2 spots on his back fins since day 1 too, but they don't look white, they almost look the same color as he is, which made me think it was discoloration.
I feed them NLS marine and sometimes frozen, and I toss in a piece of algae wafer once in a while, they seem to like that. Tank is crystal clear, last I checked everything was fine, no ammonia, normal everything. Temp is 79 to 80, good filtration, filter is for around 50g and the tank is only 20g.
Any thoughts?

