Neptune's Harvest Fish & Seaweed Fertilizer Neptune's Harvest Organic Fish/Seaweed Blend Fertilizer gives you the best of both products with a perfect blend of fish hydrolysate and seaweed, ensuring a complete fertilization program. Growers using our fish/seaweed blend fertilizer on a regular basis have reported increased marketable yields and improved shelf life on fruits and vegetables. Fish and Seaweed are known to build the natural sugar in plants. Flowers and foliage will be stronger and more colorful. Blooms will be more plentiful, fragrant and longer lasting.