Lighting.
For a successful planted tank you must have light. A recommended starting light level is 2 watts per gallon; note that these are florescent watts. There are some plants that will survive and possibly even grow at lower light levels but these plants are few and far between. Most "fish" tanks don't come with nearly enough light to grow plants. A good case in point is the standard 55 gallon tank sold in the US. It comes with either one 40 watt bulb or two 15-18 watt bulbs. This is enough light to see the fish and prevent the majority of algae growth.
As far as special plant bulbs, they do work, so long as you get to the 2 watt per gallon range. Most any color temp or
K bulb will work so long as they fall into the 5000k-10,000k range. Most people shoot for 5000k-6700k range. One thing to avoid is actinic reef lights. The blue light of these bulbs will not help your plants much if at all and some people have said they tend to promote algae growth. One thing to note is if this is your first foray into planted tanks you want to stay under 2.5 watts per gallon unless you are willing to invest the time and/or money into a
CO2 system.