I had bought two five month old Koralia 3's from a fellow reefer to put in my 75G reef tank, and thought it would be the proper flow, I was even wondering if I needed the 4's instead, by reading what the box said on it. Good thing these were only 3's, cuz when I turned them on it was crazy water movement and dont think the corals liked it. So, I was looking for someone that maybe has some 2's that would like to upgrade too some 3's even trade. You can pm me or can call me if you want. I can pm you my phone Number. thanks Mark