Great…one my tank e09 I get 16 hours on low (10 lumens) which lasts for only 2 days (2x8hrs) as night side lamp. My Quark X gets about 5-7 days on low (3lumens). The 3 lumens on quark is about a bit brighter than the 10 lumens of the tank….Maybe its the emitter…no clue really!