I know someone who has two powerheads for sale. I am looking to buy them. They are hydor koralia 425 and 400. He wants to sell them to me for $40 for both. Is this a good deal? Will I need both of them?? My tank is 55 gals.

the more flow the better do both for sure and maybe add another as long as its not blowing corals sand or pushing water from the tank your ok