well a couple of things. Filtered water through a normal type filter isn't really sufficient but it does depend on the source water. Reverse osmosis is recommended as it removes about 90% of disolved solids (TDS) from the water which could be consist of silicates and phosphates that are not removed via regular filtering alone. The remaining 10% of tds are removed inthe de-ionization process which will make the water virtually 99.9% free of tds which can contribute to algae blooms and diatoms later down the road. A UV sterilizer is really not necessary and adds virtually no benefit to a tank of your size, again you are better off spending the money on a sump or more live rock, properly quarantining any livestock additions and you won't have parasite problems.....as they will manifest themselves during the qt process.