ground cover
 

I'm looking for something that will quickly cover the bottom of my tank. The faster it'll spread, the better.

you can plant Dwarf Baby Tears, if done correctly it will form a beautiful carpet in your tank

I didn't have good luck with dwarf baby tears and I have moderately high light...

Dwarf sag worked well for me. (low light it grows to 6 inches, but in my higher light tank it's only 2 inches tall.)

anyone have experience with pygmy chain swords?

I just ordered some, so I can let you know in a couple weeks...

If you have sand, dwarf hairgrass is good...

Pygmy chain sword is a great foreground plant. It looks very nice and it spreads runners like crazy. I had it in my 55g and I now have it in my 120g ;-)