20W floresent light and corys in the tank.Few questions
What type of lighting? How many Watts?
What fish do you have in the tank?
The right species of plant really depends upon these conditions.
20W floresent light and corys in the tank.
20W over 30 gallons = very very low light.
Java fern and java moss only. Expect it to grow very slowly if at all.
If you want to grow other plants you will need to get new lighting for the tank. You'll need to be looking for a somewhere around 60-90 total watts to grow most plants.
The cory's will love you for adding in plants.