Features of Mark 4 Fluidised Reactors 1.   - Water inlet with Micro Filter to remove debris. 2.   - Water flow control tap on inlet supply. 3.   - Outlet pipe. 4.   - Port for optional pH probe. 5.   - Top and bottom sponges to retain media            (bottom sponge not shown for clarity) 6.   - CO2 bubble counter with non return valve. 7.   - Recirculation pump. 8.   - New lid section is completely removable for          easy filling and cleaning. 9.   - Acrylic body showing central down pipe. 10. - Perforated diffuser plate below sponge. 11. - Cone base for even water flow through plate.