RLSS stands for Reef Life Support System
RLSS R8U:
Measurements: 400mm x 310mm x 550mm (15.75" x 12.20" x 21.65")
Power Input: 100-240V, 50-60hz AC converted to DC Power
Power: 40 watts max.
Air Intake: 900-1800 L/h
Recommended for 1000L-2000L Aquariums (264-528 gallons)
Switchable Pump Design Universal Skimmer Body.
RLSS R8I:
Measurements: 305mm x 210mm x 550mm (12" x 8.27" x 21.65")
Power Input: 100-240V, 50-60hz AC converted to DC Power
Power: 40 watts max.
Air Intake: 900-1800 L/h
Recommended for 1000L-2000L Aquariums (264-528 gallons)
Space Saver design with small footprint.
[video=youtube_share;i9jDcgvQvBc]http://youtu.be/i9jDcgvQvBc[/video]
looks like the R8U is slightly bigger body with a universal pump motor mounting system,so that the pump can be changed with a different type,not sure why you'd want to do that though,unless by it having a slightly bigger body,maybe the company has a larger size pump to make it suitable for a larger tank ????
both have the same DC pump motor with speed control,both are rated for the same size tank,the R8I has the pump mounted inside the body the R8U does not....both look great and both are very low power consumption