5 gallons is a fairly small tank
11 watts over 5 gallons isn't actually that much even if you calculate it at around 2 WPG
what plants do you currently have inside the tank ? : )
*btw c02 might not be that usefull at that lighting level..
here are a few of the plants that a friend of mine advised to me for my 2 gallon nano
link to my tank
the folllowing are fast growers that are usefull against algae
elodea/hydrilla, najas, ceratophyllum(hornwort), riccia, duckweed,
bacopa caroliniana, hemianthus, Echinodoruses tenellus, quadricostatus and xinguensis, Sagittarias pusilla, subulata and platyphylla, Rotala rotundifolia and Limnophila sessiflora, Hygrophila repens, Heteranthera diversifolia, Lagarosiphon madagascariensis, Glossostigma elatinoides, hairgrass
*just google the names to see what they look like and their needs
*glosso, hemianthus, sagittarias, hairgrass are some of the species that can serve as a carpet
but are not easy to grow IMO (except for the sagittaria species (well some of em))
hope this helps
