Well all it really says is this
KENT MARINE BLACK WATER EXPERT contains natural humic and tannic acids that simulate water conditions found in the Amazon region of South America, Southeast Asia and Western Africa. Excellent for Discus, Tetras, Angelfish, Barbs, Gouramis and all other soft water fish. Encourages spawning and aids in the hatching process.
but other people said it aids in healing as well.