CO2 has a great effect at 2watt even less, down to 1 watt/gallon IME.
I've been squawking about this issue that Gloss, hairgrass and other plants don't need 1/2 the light folks use on it of often advise.
At the AGA, Claus mentioned this.
You can go to the Tropica web site to see a nice somewhat technical write on the subject of CO2 effects on a low light aquarium.
A controlled study is nice and they used one plant, Riccia, which is a rather odd plant, from an odd group, but I found the same results several years before hand in practical hobbyist terms with about 60 species of plants. I would extened the species list out to all plants.
Amano has a similar opinion.
I've seen some very nice gloss carpets at 1.5 watts, a 15w light on a 10 gallon tank.
The Gloss looked as good as any I've seen.
Steve Dixon's 125 has 2.1 watt and it's the T-12 bulbs with a few little 9 watt PC's and a regular reflector. The tank is 24 inches deep.
His Gloss and tank looks great. It was on the cover of the first issue of Plant Aquarium Magazine.
I like Dwarf clover. It's nice.
E. tennellus is nice, Cuban chainswords,
Dwarf lobelia is the easiest IMO/IME. I've seen it for sale here a few times.
Anubias nana is nice but cost a fair amount. Crypt x willisii is another nice plant. Those are all nice foreground plants that do well.
Regards,
Tom Barr