I have always had good luck with standard lights and anacharis (elodea/egaria), in a well established tank the main problem was always keeping up with it, I would harvest new growth strands of 10-12" long every week for trade off, and would trim out old, dieing strands at the same time.
Make sure you get Elodea densa and not E. canadensis, E.nuttallia, or E. callitrichoides, the last three are pond plants and will get spindly, turn yellowish, and fall apart in tropical tanks, they require a brighter light and lower temps.
Unfortunately I can't tell the differense and the callitrichoides (from Chile) is lately often sold for tropical tanks, this may explain the problems you have had.
This is densa, it has leaves that are a little shorter and broader than the others and they tend to be closer together.
