Galvanic isolator

I have two stainless steel submersible pumps in one large sump. One pump has been disabled due to a heavy red deposit of crud on the pump (capacity 360 lit/min). I assume this is due to the galvanic action in what is a weak electrolyte (possible the water has a high iron content) which is magnified by the common earth. It looks very much like a plating process.

would a galvanic isolator fix the problem and should I use one on each pump earth?

Any info very welcome.