The selection below focuses on plants that can grow well in tanks without injected CO2. Some are sold in tissue culture form, which has the advantage of being free of algae & snails. You also typically get a very large number of plants in a single cup: a single TC cup of carpeting plant can cover the foreground of a 2 feet tank easily if one takes care to plant the small plantlets separately. However, compared to adult sized plants, tissue culture plantlets are more delicate and have better success if the tank has already been cycled and the substrate allowed to mature somewhat. This is especially applicable to ammonia rich soils such as ADA aquasoil - TC should be used only after the initial 2-3 weeks have passed.