What makes Kelpy the best fertilizer for indoor plants? It's easy to use indoor plant food made form wild harvested Canadian kelp. Kelpy won't cause salt build up and can be used year-round for happy healthy plants. Kelpy is food for plants that helps promote new growth, bigger leaves, more vibrant colours and builds resistance to pests. Making it the best plant food. Our kelp is harvested from the frigid coastal waters of British Columbia where it grows more than 2 feet a day from the rich mineral glacial outflow that feeds it and is cold processed (never heated) to keep all of the vitamins and nutrients intact.