An airline T joiner for aquarium is a small plastic accessory that is used to split an air supply line into two separate lines. It is typically used in aquarium setups that require multiple airstones or air-driven devices, such as sponge filters or air-driven protein skimmers. The T joiner is made of durable plastic and is easy to install, as it simply slides onto the air supply line. It helps to ensure an even distribution of air throughout the aquarium, and can be used in both freshwater and saltwater setups. Airline T joiners are a cost-effective and practical way to enhance the aeration and water movement in aquariums, which can help to improve the overall health and well-being of aquatic animals and plants.