Sorry if it's abit vague I've had no sleep ha I'm planning to do the barrels like how Uarujoey (if that's how you spell it) tank will drain in to the first barrel being mechanically filterd first then into k1 then pass through a 3 inch pipe then into the 2nd barrel where it's heated then pumped back to the tankJust sharing my opinions, may not necessarily be right. For the 2 barrels how do you intend to run them. Any sketch/pictures will be good. Don't quite understand how its intended. For the pump (too many to choose from), likewise for medias type & quantity - kinda subjective. Perhaps can look at type & cost efficiency. Cheers