Cornish Cobles.....

[Sp00ky]

If washed really really really well, will they be ok in a tank?

I have half a bag in the garden and figured i might use them in a cory tank to make hiding places for em.

They are a bit sandy, but would wash and soak them well if they are ok to use.

 

[Breeze7050]

http/www.fishforums.net/index.php?showtopic=55806 - I would check that first, I personally don't know what cornish cobles is!
I would also recommend boiling it for at least 20 minutes to get rid of any nasties it may hve acquired outside! HTH!