Agreed with AC
. I have had success with Rotala W in the past, but I had very high light, 35+ppm CO2
, and was dosing PPS Pro. If the bottoms are melting, your lighting is probably not high enough for this plant. Also, on that large of a tank, it would be hard to consistently keep your CO2
elevated above 20ppm, unless you are changing the mixes every few days consistently.
I also found the best way to get it to color up was to make the tank N limited. I got some great oranges and pinks out of it that way.