Thank you for the quick response and great info.
What about doing with small foreground plants (hc)?
Well, 20 longs aren't too deep so that is doable. You will probably need Co2 for them though. Well, let me correct that, those carpeting plants grow better under higher light, higher light normally needs Co2.
I'm sure it's possible to find that happy place of high enough light to grow them without high enough light to require Co2, but I don't know what lights you need to get there. Even if you did find that spot...I fear they would grow at a snails pace without Co2. Welcome to the technical side of planted tanks, lol.
I have a low light tank, I fail at dwarf hairgrass and HC, and I am using Co2
. Just not enough light for them.
Drawf Sag grows fine though. I would start a new thread in the lighting section, ask them what lights you would need to grow that plant in that tank, and if you would need Co2. I simply don't know the answer to that.
To reiterate, all root plants will benefit from a dirt tank. High light, low light, Co2 or not.