there is a synthetic fiber filter pad available to us that strips many impurities from tap or tankwater. check this out:
poly-bio-marineread the whole site, its very interesting stuff.
i think that youll find this material to have excellent sorbtion properties. im thinking that
maybe it could be set-up inline just before the pond to remove (everything it claims to remove).
this product says that it removes heavy metals. isnt chlorine a heavy metal? you might want to correspond with the company to find out about the clorine removal first.
ive been sitting with this products page in my favorites for quite some time now. ive been waiting for a good reason to suggest its use and i think your situation might be perfect for it. that is, if you didnt want to purchase an expensive tapwater modular filter unit.
what do you guys think about this stuff? does it sound like it warrents further investigation?