powder blue tang worries

Hi.
I've had a marine aquarium a few months and just bought a powder blue tang. Now i've got him i've read that they are prone to ich and he seems to scratch himself on the rocks quite a bit but i can't see any marks on him. he feeds off the bottom of the tank a lot and sometimes flakes that i put in. he swims around quite a lot but his colour is more grey than blue and he was like this when i bought him. should i be worried about him and trwat him for ich. whats the best way to do this as i've got clown fish, yellow tailed damsels and firefish and they've all been happy and healthy.
Any help would be greatly appreciated.
Thanks
Sian

atnixon said:

They are very prone to ich yes and the scratching is a good sign that something is not right. However, you need to be able to see whats wrong before a suggested routine of treatment can be suggested. Of course, for ich, start having a real close look for white spots, and the immediate you see something, you should remove the tang into a quarantine/hospital tank and prepare for treatment depending on what is seen as wrong...

Niko

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hi.
thanks for getting back to me. i've looked on the internet and i'm getting more paranoid. My tang is eating and darting around but still scratching now and again. I can't tell if his breathing is quicker as i don't really know what it should be like. There are no signs of grainy spots of any colour so does this mean that i shouldn't attempt to move him out unless i see some. All my other fish are looking really healthy and i'm also worried that they might catch something.
thanks again

Hi.
I'm not sure if you can see from these piccies but he's got a few darker marks on his body although we bought him with some of them i don't know if there's more now. he's swimming around a lot more today and eating and there's still no sign of any spots. i think he may be scratching less as well.

2 clown fish, 2 yellow tailed damsels, 2 purple firefish, 10 hermit crabs, 5 turbo snails.

ph 8.1
ammonia 0
nitrite 0
nitrate 5 or below

its 300 litre tank

Hi.
thanks again for all you help. He's the same colour as when i got him. (wish i'd researched before hand his proper colours, i saw him in the shop and wanted to take him home.)He was in a standard very small tank in the shop. To me he looks malnutritioned. The darker areas aren't reaised, they just look like blemishes and if anything i think they look more indented.All my other fish are leaving him alone. He's still scratching a bit.
What does the garlic do? Will it effect my other fish if they eat the food with it on?
Sian