I am curious, as I have been trying to get my chaeto to grow and through research, I was able to piece together that a 23w 6500k bulb works the best for growing it... I currently have a 15w daylight flood cfl that has a rating of 5000k and it hasnt grown much since I added the bulb. I went out today looking for a 23w 6500k flood, but the biggest 6500k I found was 18w... I also found a 23w 5000k bulb..... For those with experience, which would be the better bulb? the 23w 5000k or the 18w 6500k bulb? Or should I just buy 2 18w 6500k bulbs and mount them both...I am gonna try as many combos as possible of lights, I need the chaeto to start pulling some nitrates... I bought the higher watt bulb, the 23w 5000k bulb, but can bring it back if its definitive that the chaeto will grow better under the 18w 6500k