My first question would be what kind of chemicals have been used in the tank for medicines, cleaning, maintanence, etc. If there were no harsh chemicals ever used then you may be able to do a simple vinigar bath, or very mild bleach solution bath to it to get it cleaned. The chemicals would be my first concern, second concern would be any amount of toxins like ammonia that may have leached into the silicone on it, not sure if this can happen, or how much it does happen, but I do know that any predator, or omnivore like that is going to produce a lot of waste. The water that they live in doesn't bother them to a point, so they can probably tolerate higher ammonia levels, now we all know that our saltwater fish cannot. I would hate for you to be constantly battling ammonia or some other toxin because it is leaching out of your tank seams... just some thoughts, not sure if that helps or not... Maybe take it and clean it very well, throw saltwater in it, let it run bare bottom, nothing in it for a few weeks and do a regular test ont he parameters to make sure it is safe to use, then turn it into your refuge... JMO