Its worth just giving it a rinse to remove any fine powdery residue. As its gravel, the grain size is probably 3-5mm, so a lot of the finer stuff will already have been removed. 2" is fine. Anything more than that and you are venturing into the realms of a DSB (Deep Sand Bed). While this isn't a bad thing, I'd suggest you read up on them before you decide whether or not to add more sand. To give you a brief summary of them.
Where live rock provides a home for aerobic bacteria, which produces nitrates after it feeds upon ammonia and nitrites, the lower regions of the DSB provide a home for anaerobic bacteria. Because of the low oxygen levels and lack of water movement, the anaerobic bacteria evolved to feed on nitrates. The benefit of this is obviously the reduction of nitrate levels in the aquarium, which for corals and invertebrates is a particularly good thing. The only drawback with a DSB is that they can "crash" if not maintained. Fish poop and other organic waste will settle in the sand and the pollutants begin to build up. For this reason, the sand bed needs to be vaccumed with a gravel cleaner every so often, to remove excess waste.
The only problem is that when you clean the sand, you disturb it and kill off the bacteria in the section cleaned, which is why you have to perform the maintenance a section at a time, to give the bacteria a chance to recolonize the disturbed sand.
If you have a sump, you could create a refugium in one of the sections and have a DSB in there. If you also put filter wool over the baffles to prevent poop and uneaten food from entering the DSB, you'll find that maintenance is virtually removed for the equation
Something to consider anyway.
/www.arkpetsonline.co.uk/coral-sand-4kg-p-1321.html?wizid=2iv4h7editjqlthpd7vqe0oed1
