Yup. Sounds like you need a clean up guy! Get a snail. I've got two bunches of elodea that I just keep weighted down. I hide the bottoms behind decor so you can't see that they aren't rooted. I also have a banana plant, mondo grass ( which I know is typically a bog plant but its doing fine for me since three months) and christmas moss tied to some rocks. The substrate is sand and gravel mixed. My tank is shy of 4 gallons and I use a desk lamp with a 10full watt, full spectrum flourescent bulb. For the pass three months I haven't dosed with anything and my elodea has needed to be cut back twice. Everything is nice and green and happy. My snail scoots around slurping off whatever might start growing on the leaves, and takes it upon himself to trim up browning leaves. I love it! The added plants really help facilitate a strong nitrogen cycle as well. There are super simple plants that are hungry for fish poo so do some research on what those might be, as well as what works for your lighting situation.