Again I'm calling on the experience of some one here at AA. Ended up going elsewhere to settle the filter question. Now about the lighting. Metal Halide is the cheapest way to go initially for my 20 Gal. build. $100 for a 175 W. 14000K system. Or $400 for something nearly equivalent in the LED Dept. Leaning toward the LED's as I'm not a big fan of the heat generated by the halides.Would very much appreciate any serious thoughts on this topic. Thanks