arm waving is perfectly normal behaviour in bearded dragons. it is used mostly during breeding, but my beardie does it when he is about to pouce on his food.(crickets)
G'day Neven - I've kept and bred beardies for a while on Sand without any probs. You just need to be careful not to feed them on it. Can be a bit inconvenient but if looks are important it'll be ok. Also, when beardies get older they tend to show more and more colour, particularly around the ears and head in general. If he's stil, pretty young you could end up with a very yellow phase beardie. Look forward to getting him into the sun come summer time!