I would definitely replace it then. Who knows whats in it. I am currently removing the sand from my 29 biocube. If you have livestock in there make sure you do it slowly. I may be doing mine overkill. I have been removing my sand bed for 3 weeks now, a little at a time.
My over flow box came loose from the back of the tank. So I had no control over water flow to the sump. So I'm doing it all at once. Thanks for the help.