PLANTS FOR DISCUS TANKS

I have a 250 l.itre discus tank which I would like to p.lant out. Can anyone advise me on what to use and how to go about it. Unfortunatel.y the temperature is 29-30C which is quite high. I am getting a Dupla CO2 unit for the tank. Are heating coils beneficial to keep the substrate heal.thy? How will I go about cl.eaning the gravel. as I would like to add the Dupla laterite. The water has to be very cl.ean for these fish so some form of gravel. clean has to be done.