Firing up a setup for the first time in 3 years.

[asylumdown]

Honestly I would toss the sand. For all the potential problems it could cause you at this point it's probably worth 40 bucks to buy a new bag of caribsea special grade or something similar. 1 40 pound bag is probably enough for a 40 gallon isn't it? The rock is definitely salvageable, either by curing/cooking it in a tub for a couple months until you stop seeing nutrients in the water, or by speeding up the process with either the muriatic acid or bleach methods that are floating around on the internet.