These premium quality pre-filter foam sponges quickly and easily attach to the intake tube stem, preventing small, baby, or weaker inhabitants from being drawn into the filter. This is a must have for all shrimp tank owners and anyone else who has baby or small fish in their tank. Installs in seconds and lasts for months or even a year, depending on contents and load factor of your tank. Aids in biological filtration. Traps debris and prolongs the life of your filter media