You'd want to use oak leaves or indian almond leaves, they don't really make your water THAT black but rather it takes on a brown hue. The leaves are actually rather pleasant looking and in the right amount will do a very good job putting your softwater fish in breeding condition. The leaves will slowly drop the ph and soften the water. Indian almond leaves also have medicinal value, I use them while treating any infections or disease.
A tank of leaf litter, apistos and tetras can look very nice. I'll show you the pics of my tank later on, it's too early to take pictures right now the lights in the tanks haven't even come on yet.
In asia the leaves are made into tea to treat liver related diseases.It's also said to be a aphrodisiac, and has de-toxifying properties. Suriname's traditional version of the medicine has been used to treat dysentery and diarrhea.