hello sumo since last I wrote I have been on the net and sadly cant find anyone selling manders varnishes any more,so I have been on the ronseal website and asked their technical services department what they have got. they say that their decking stain is completely harmless to fish and does not leach out any thing after it has dried . so as long as you dont allow any to get in your pond while drying, your fine .hope this puts your mind at rest .(ps was going to e mail their reply to you but you do not accept e mails. grandad.aka brian.