Do you know what chemical was in them.? Chemicals stored in dums and ibc have a bio rating on the label 1= low . Water based glues would possibly be white glue and wood glue and im sure we all have had those in our mouths in the school years. Chances are the product was an elestomatic paint coating used to top coat foam roofs. Once the product dries it is safe (maybe) . How many people use rain water from roofs? Just be carefull and know what the product was and clean well. You might want to fill and drain several times before fish use.