OK sorry, i didnt mean to make you panic. send me a piccy of it via email ( i will pm you my address).
Im not saying it definately IS whitespot but the mark made me feel it was possibly the mark left behind when the whitespot parasite falls of the body my powder blue tang is just recovering froma whitespot outbreak after its introduction to its new tank and the makrs lefton its body could look simialr. I will need to see a photo to be sure though.
The other reason i asked about tank size is due to the future happiness f this fish, tangs grow large (Regal tangs get VERY large) and a 40 gallon is just not going to be enough im afraid
100 gallons (thats uk gallons.. 120 US gallons) minimum for tangs and even larger if possible. I currently have a 100 gallon tank with 2 tangs and its simply not large enough
I am having to upgrade to 220 gallons after christmas just to accomodate these fish as the current room is not enough for them.
Im sorry to say that if your tang doesnt have whitespot now then its highly likely to get it in a tank of this size sooner rather than later
Tangs should also be added last to a tank as they are very territorial and can get very aggressive. My emperor tang and Powder blue were both the last fish to be added (with the exception of the asfur in between and my Comet which they ignore as its keeps to the darkeness).
I think you may well find trouble ahead if you try and add anything that is remotely similar to the tang in size or colour once the tang is settled in and established. (Dangerous to add a dwarf angel IMO )
You asked me if it was possible to ad a yellow tang now or should you wait. My responce is that it should not be added at all as they are likely ot fight (my emperor and powderblue did) and in a tank which is so small they are liekly to either kill each other or stress themselves out and get whitespot.
This forum has a wealth of people that know alot about this hobby. I really urge you to post questions on fish etc here before purchasing. Making a simple single purchase can wipeout the entire tank via whitespot or agression etc so research is essential before simply going out to get a fish you know little about.
Im afraid to asy that many shops are simply not to be trsuted as i have seen all to often how most shops will sell fish that are completely unsuitable for the persons tanks and cause a multitude of trouble. If you ask here you will get a thruthful answer not loaded with any financial gains etc. Im not getting at you in particular and if it seems this way then i appologise but its more for people that are going to read this over the coming days and weeks. If this makes a single person think twice before buying a fish/coral they havent research then i have done what i have set out to do.
Good luck with the tang, send me a photo and i will try and diagnose it for you.