Recently I did convert my redsea tank's ATO to a refugium as I wanted to grow frags in my refugium compartment of my sump so I needed an alternative place to grow chaeto. First off, I needed a hang on overflox box as I did not want to drill any holes into the ATO tank. I also did not want to go the 2 return pump route as one pump dying could lead to flooding of water which is very dangerous. I am using a Oase 800 return pump with a J hook pipe to transport water from my skimmer compartment into the refugium For the lights, I purchased a cheap china brand light which has a timer function! Very worth it lights I must say considering it has many different led diode colors which is beneficial for the chaeto as it does not only require red lights to grow chaeto. I tied it up using some cable ties and fasten them to the piping in the sump. Lights are in a plastic housing with a metal plate top so the heat is easily dispered upwards. Some diodes are dimmer than the rest as those are the uv diodes. So far my external refugium's chaeto is growing like mad and I noticed many pods take refuge in there. Glad this project was a success, as I comtemplated for the longest time on setting this up 🤣