Here is a product sold in LFS, sounds like it is more for the fish than the plants.
Blackwater Extract contains trace elements, vitamins and extract of peat. It replicates blackwater conditions by creating clear, "natural", Amazon-biotope conditions in the aquarium. Blackwater Extract promotes fish activity levels and is an excellent conditioner for all soft-water fish including Discus, Angelfish, Tetras and Killifish.
Principal ingredients include vitamins B2, B6, B12, nicotinic amide, panthenol, biotin, and peat extract.
Add 2 teaspoons (10 ml) for every 10 gallons (38 liters) of water. Replenish monthly or with every water change. In areas with very hard water, double the amount used.
8.45 oz. (250 ml) treats up to 250 gallons (945 liters).
