Thank you for advice, we had never heard of them before either, and poor hubby nearly died when he saw something swimming in the loop 🤣🤣🤣 Google identified them! There is no obvious light other than from toilet as we do leave the lid open usually, but it is quite a few metres away. Hubby has been fly spraying with pyrethrin meantime! We are about 3 years in and these are new! The worms are doing a pretty good job on their own! We have an aquatron type arrangement for seperating and 4 chambered collection unit!