missings fins

[flame82]

i have few fish in my tank that seem to loose a horizontal line of color in their back fin. This occurs every few months just for a day or two and the next day all fins are back to full color. anyone have this same thing happen to them that the fish some how makes part of their fin clear in the morning and back to full color at the end of the day. i have not found anything on this and i find it wierd but interesting at the same time.

 

[AR15 guy]

What kind of fish is it?

 

[flame82]

they are a salfin tang and coral angel and today both of their fins are back to normal just happend yesterday for about 10 hrs or so and this morning back to normal so i was just curios if anyone else had seen this, since i not worried about them being sick they are both healthy