Your substrate should hopefully be a source of iron. The size of the
gravel should be fairly small to help the plants take root. There are
actually specialty substrates just for aquatic plants, do some research
on an online retailer like www.thatfishplace.com and you will quickly
find them. You will also need a good plant fertilizer, I like the
Seachem product line. You need to get fluoresent lighting made for
plants. I use the Zoo Med tubes. Oh, you need a carbon dioxide
source. I do it using a yeast and sugar solution in a DIY generator.

It is actually a lot of work to get everything set up. Are you sure
you want to do this?