[bigben2k]

You've got galvanic corrosion, big time.

Probably red from the Iron, and blue from the copper, hence the brown color.

Copper and brass can get along very nicely, but the iron is throwing everything off. No filter will fix this.

I have yet to read about good solutions to prevent galvanic corrosion, and while the idea of grounding everything seems to make sense, it isn't a foolproof solution either. There are electronic solutions to this, but also just as many claims of scams on those units.

If you removed the iron elements, and use a mag drive pump that has a plastic impeller housing, you'd be back on track. If you were local to me, I'd gladly lend you my LGPC 2-MDQ pump.