I have Red Sea max s400 that came with 2 sicce psk return pumps. Tank has been up for only 10 days. 1 of the pumps quit working over the weekend. Red Sea had me disassemble and clean it, but maintenance is not the issue I noticed with pump apart and impeller installed that impeller is not running smoothly and making grinding noise so I’m thinking that the bearing in body of pump is bad. Another thing I have finally figured out that humming noise from tank is not return pump but is coming from circulation pumps with 1 out and other shut off tank is quiet. Also there are no suction cups for feet on bottom of pumps. Are they supposed to come with? That would definitely make tank quiet. I’m currently waiting for RedSea to get back to me to resolve bad pump issue.