That's certainly a possibility and may explain why they are flashing.
Try adding some charcoal to your filters, cleaned before-hand of course. This should soak up any residual chemical in the pond.
I have used presure treated timer around my pond, coated with Ronseal wood stain. I never had a problem with it once it had dried. I think the Ronseal traps the nasty stuff inside the wood.
Posted on Mar 31, 2005, 1:48 AM from IP address 213.120.101.21