You have an aquarium with fish but have always used plastic plants as the easiest option. If you'd like to try some real plants, consider these. Anubias nana is a slow growing, small plant, but is very easy and worth the wait. Anubias Angustifolia is a taller plant and also easy to grow. It does tend to attract algae, so do watch for that.
Anubias coffeeholic will flower underwater and has interesting leaves. For a floating plant, consider Ceratophyllum demersum. You'll need to watch for stray leaves, though, that drop to the bottom. Sweet flag, which grows in wet areas, produces a sweet jelly. Look for it among our wetland plants.