These root tabs with Osmocote Plus are great for feeding plants that uptake nutrients from their roots in the substrate. Use aquatic tweezers or your fingers to push the tab into gravel, sand, or any type of substrate near the plants that require fertilizer. Osmocote Plus is safe for fresh water aquarium inhabitants, provided they are not over-dosed. There are many factors that determine the correct amount you should use. Please do your research and understand how much to dose your specific aquarium before using these root tabs.