Sagittaria can send out a runner with a new plant every week and its runners can send out their own runners after they get 3-5 leaves. You won't get a carpet, but it's something to look into.I've seen pics of planted tanks with the bottom completely covered with plants with none of the substrate visible. Can anyone tell me what type of plant to use to do this?
Dwarf sag will fill in good, but if the light isn't strong enough for it, it will grow taller than what you would think. I had some in a low light tank that I used as a background plant (10 gal) that grew 10inches tall. What you see in most tanks is some very high light plants. With that you would have to have a good dosing regime of ferts and CO2.