i've got an 8w T5 14,000k over 50cm x 28x 30 deep and growing ambulia and cabomba well. Also twisted val, riccia, duckweed and tiger lotus, hydrocotyle and 2 new crypts. Plants not doing well are java fern (though new babies are very green), and bolbitis/congo fern - jury still out on that plant but the issue could be not much current making it sad. I started a thread asking about these lights and the consensus was that mine was within the range of OK light for plants, though generally suited for marine.