Water sprite (Ceratopteris thalictroides) grows very fast to help soak up extra nutrients and can be left floating. I read somewhere on the forum that since its floating that it can soak up CO2 from the air.
I don't have much experience with planted tanks but wouldn't it be cheaper in the long run to setup CO2 then dosing a 60gal with excel everyday?
If you're looking for a easier carpet plant I suggest Echinodorus Tenellus (pygmy chain sword). I had a low tech setup with DIY CO2 and a couple compact fluorescent and grew a carpet very easily, especially for a noob like me.
Loved how you incorporated the golden ratio to your aquascape by the way. Looking forward to the updates. Subscribed