Hi,
Welcome to Simply discus! If its heavy metals I would think just an RO filter would work fine.. these are usually run to a water storage barrel where you would aerate and heat and pump to a your fish tank... usually 100 -200 gallon per day units are used by hobbyists.
First thing I would do is have your water tested so you know what you really need to filter out....if anything.
Hth,
Al