Dark areas?

[causeidm]

I purchased a yellow eye tand about a month ago, I kept the tank in a quarantine tank for one week before I placed it in my 29t eclipse tank. About a day after purchase I noticed a few small white spots and one moderately larger white spot, which I treated for parasites. Now after he has been in the 29t for almost 3 weeks I am noticing dark areas starting to form in random areas, this si quite concerning as I have NO IDEA WHAT IT COULD BE?! It may be due to it's diet while in the quarantine tank, I was feeding it formula 1 instead of formula 2, but I don't understand why it would be happening now 3 weeks later. The tang also likes to squeeze between the live rock, could these be scrapes? Thanks in advance for any help you guys can give me.

 

[causeidm]

This is deffinately my fault for trying out a new fish store, they have a good reputation, but they obviously give horrible advice. I told them everything about my tank and they said it was the perfect size for the tang. I do a water change of 1/4 of the water every month and small water changes everyonce in a while throughout the month whenever I get bored. I use spring water from the grocery store because my apartments water tastes funny so I don't trust it. The treatment I used is called ICH X-tinguisher and is suposed to work within 3-5 days, according to the fish store, but the label says there will be improvements within 3-4 days, the fish store also said that it would not harm invertabrates, though I should have realised when I heard this that they didn't know what they are talking about because the active ingredient is hydrogen peroxide. I am planning on upgrading to a 55 or maybe 80 gallon tank over the summer, and the fish is clear of all white spots, it just has these nasty looking dark ones, especially around the head. If you think it's the tank size causeing it, I will donate it to my friends 80 gallon temporarily, it is currently the only fish in my tank besides a small damsel that I've had in it since november.

 

[causeidm]

Just wanted to let anyone who looked at this know that I did a large water change and found that my salinity was at 1.026, so it is now 1.022 on the dot and the Tang is progressing wonderfully. The dark spots it was developing are slowly vanishing, it is eating voratiously, and it is spending fewer time hiding in the LR.