i was thinking of this oneDutchAquarium said:light isn't the only thing playing a role in plants. Think of co2, fertilizer, and lighting forming a triangle. If your missing one of these you will have limiting factors. Java ferns and java moss can be kept with carpeting plants, but the majority of all carpeting plants want high ferts, co2, and high lighting while the ferns and moss want very low levels. Also, what fixture have you decided on going with. leds and flourescent will probably be the best for you. Your going to look for a spectrulm of around 6500K for both lighting system. this is the level plants grow in. Also, despite what many people on here will tell you and certain other websites, don't look at the wat system when selecting a light. While you can get away with using this system in a 3 gallon, watts are very inaccurate and you should use the par system.