Brown => green is not an improvement.

That might mean that dirty pond water warmed up and became algae-filled pool water. Of course, it might be something else, but it's unlikely that pond water has significant levels of metals. Of course, if the fire department tanker was badly rusted, that's another story.

Doesn't matter: trying to clean up very cloudy pool water (green OR brown) in an Intex pool is a weeks-long project if you have the standard Intex filter.

Your best bet?

Cut your losses and dump it!

Fill what you can, follow the Super Simple Recipe, and treat it as a splash pool till you can get it filled with clear water. Do *NOT* let it turn green! The Intex pump & filter systems are barely big enough to maintain clear water; they are NOT big enough to clear swampy water in your lifetime.

Super Simple Recipe here: http://pool9.net/ssr/

. . . membership updated.