RODI SETUP: It is said that reefing is simply about keeping good water. Whilst one could argue there are many other aspects, water quality for sure is key without it you wont be going very far. Hence, for my new set up I wanted to make sure that I had good quality RODI water. So first off why would one need RODI vs. Dechlorinated water? Singapore is awesome, and they have amazing quality water. I get 68TDS for my water from the tap, that is typically cleaner then rain water, Great job PUB Singapore! Still for reef needs 68 TDS is still too high. So what does an RODI system do? Firstly RODI systems remove sediments, silt, clay... (it's amazing just how dirty the sediment filter gets from tap water!). Typically a four stage system will have one 5 micron sediment filter. (Bigger systems can couple this with a further 1 Micron filter). Secondly the carbon filters and RO membrane(s) remove any unwanted chemicals like chlorine, chromium, pesticides. The DI resin typically focuses on the removal of heavy metals like copper as well as some acids. Combined they remove impurities, microorganisms, disinfection byproducts, inorganic chemicals, organic chemicals, and even naturally occuring radioactive nuclides! Now whilst Declorinated tap water is okay to use short term all the above elements even in extremely small ppm/ppb will build up over time (Silicone even absorbs heavy metals). This will start to cause issues (typically algae related) for you. My system is currently 7 stages. 1x 5micron sediment filter, 2x Carbon, 2x RO membranes in water saver configuration (the waste water of the first membrane goes into the input of the second filter, and both RO membrane accepted water are joined together). I run 2x DI resin filters. The idea here is to hold the Cation and the Anion resins separately. Typically they deplete at different rates so only one needs to be replaced versus a single mixed bed resin setup that you replace both resins when just one of them depletes. My system also comes with a micro controller, which auto flushes the system, along with keeping track of water quality (alarms come on if water quality is poor). Flushing makes the RO membranes last much longer. In the end you only need a system that produces 0 TDS, additional stages and control systems do nothing more then make the unit more efficient. Whilst the micro controller is awesome, simple systems off lazada will work too. Hope that helps. Happy reefing everyone Sent from Singapore Reef Club mobile app