RK2 Xflo 3.5 (400-700 gallons)The most important things to consider when purchasing a protein skimmer are performance, reliability, and durability. XFLO Protein Skimmers combine all the above to deliver one of the most innovative protein skimmers available today! Dont be fooled by sleek looks, gimmicky twists, or exaggerated needlewheel performance! If a protein skimmer looks good and doesnt perform, how good is it? RK2 set the bar for protein skimmers in the public aquarium and