Slate!

[shanna]

I know that slate you get from petstores is generally okay, but what about slate that was previously used for other purposes? Can you put that in an aquarium, post washing it in hot water?

We had some slate they used on our fountain, and as steps on the ground. I took it, broke it up, washed it, but I'm wondering if it's fish-safe?

[Rachel]

Slate is usually a good choice for aquariums.

Is the stuff you have coated with anything? A sealant of some sort? Was it exposed to herbicides or other chemicals outside? These are some things I'd keep in mind that would prevent me from using it even after being washed.

Of course I'm not an expert on rocks though. That's just what I think would be best.

[durbkat]

Is slate basically rocks? If so I would never use rocks or anything for that matter in my fish tank. Because you never know what it has been exposed to. It's just like this kid I babysit for he has long 20g with 2 angelfish and so other kind of fish and he put 4 roucks that he found on the street outside in his tank and now the angels have fin rot and all the fish are not active at all. They only come up for food.

[amanichen]

Unless you're sure of the origin of a rock, don't use it in a fish tank. That applies for anything really.