This appears to be an amazon sword. Melons usually have a slightly rounder tip.
If so, this plant needs moderate lighting and iron-rich fertilizers and substrate to flourish. I recommend T5HO lights in the 5000 - 6700 degree K range (full spectrum lights) with an average of 2-3 watts per gallon to encourage plant growth.
However, be aware of the needs of the other plants as well. If you have some that require more or less lighting, then I would try to moderate it out to the point where all of their needs are met. For example, if you have a low-light plant with the moderate light plants, I would lean more toward the lower end of the moderate scale. If you have high-light plants then I would go more towards the higher end.
BTW... Nice plants!