Ive forgotten the ratio for a return pump for the size of tank is it 3:1 or 4:1 etc: and I need to purchase 2 new Koralia's for a 90 gallon tank would 2 1050's or 2 1400's be best for flow in a reef tank.
It depends on what equipment you have sitting in your sump. IMO either of those flow rates is fine.
I think the pair of 1050s would be more than adequate for a 90.
