What lead's you to believe lighting is not enough? Is this low tech, or high energy tank with CO2 ?
Could maybe run dual T5 NO,or dual 24 watt T5 if lighting is raised high enough on low tech. But remember,, that increased lighting, means the need for increased CO2 and increased fertilizer.
Low to moderate light mean's less CO2 is needed and less fertilizer.
Need to know your goal's as far as growth, and desired maint.