Thank you for your question. There isn't a conversion between LEDs and any other light source to determine suitability for the inhabitants of an aquarium. You may find the article below of assistance. There is also some more detailed information for determining LED suitability provided.
LED Lighting Tipshttp://www.drsfostersmith.com/pic/a...
If there are only fish in the aquarium, lighting is for viewing purposes only. If you have plants or corals in the aquarium, you will need to determine the PAR (photosyntheticlly active radiation) requirements of the particular plants or corals and compare that to the PAR information available for the LEDs.