I have the 2 bulb fixture from aquatraders.com on all 4 of my 40b. Works great, especially for the price. But I wish it was a wider fixture. 40B is super wide, and thats why we all have them! But makes me wish I had 2 fixtures to space out front/back. Although my stems in back grow fine and my HC up front is doing fine aswell so I cant complain too much.