You wont get the same lumens as a 400w MH or anywhere near it with the 30w. I have three 30w's 1-2" off the water in a 30" deep tank and the lighting is a nice lower level very natural looking clean light. If you want to go bright and hang them high get 50 or 100w's. If you want stadium lighting like two 400w MH you're going to have to go higher wattage then anyone that's posted has tried.In deed very helpful. I am looking at possibly replacing my 2 400w mh that I have on my 240 african tank. I currently have the MH 24" off the water in some big 20x20 reflectors and it covers the whole tank. I am thinking that maybe 3 of those 30w floods 12-18" off the water should cover the whole tank and be as bright...thoughts from the ones who have them already. Tank is 8x2x2.