Petco Purple Aquarium GravelPetco Aquarium Gravel is ideal for freshwater and safe for marine aquariums. This high quality gravel has colorful, durable coatings specifically developed for their permanence and non-toxicity. The gravel is processed to remove potentially harmful debris and materials. It will not affect the water's chemistry, nor harm any fish, invertebrates or plants. Can be used in aquariums, ponds, water gardens and terrariums.