I don't think I'm going to get a Ray II. I've already tried DIY CO2 and it didn't work for me. Also, I doubt my dad would want to spend $200 on a pressurized CO2 system. I'm trying to avoid all of the algae so that's why I'm going to downgrade to a FugeRay. It should put me at low-medium correct? Will it be enough to grow rotala species like indica and wallichii well?
You might be able to use Excel as a carbon source for the plants, and grow those plants with the FugeRay. They will grow slowly compared to what they do with more light and CO2, and they will tend to just be green plants, without red or yellow colors on the leaves.
Plants require nutrients to grow. The more light and CO2 you add, the more nutrients they need. A low light tank will still use nutrients, but a rich substrate or reasonable fish load with associated feeding can sometimes sustain plant needs. A low light version of EI can be applied very easily, give your plants the nutrients they need and not go overboard. You will be able to modify the whatever dosing you do by measuring phosphates and nitrates. If you have excess nitrates and phosphates after your waterchanges, reduce dosing.
Try the calc below. It has a low light dosage option.