The MultiLux LED is a high-performance, energy-saving LED light unit for your JUWEL aquarium. The Old T5 lights units can be completely replaced with the NEW MultiLux LED light units. The replaceable DAY and NATURE LED tubes create an optimum light spectrum for plants and fish, while saving up to 50 % of energy in comparison to T5 light units. T5 bulbs will not work in this NEW light units and LED bulbs will not work in the OLD T5 units. Both LED bulbs must be inserted into the unit for the system to work, It will not work with just one tube. 14 Watt MultiLux LED 80 cm fits for Rio 125.