Assuming you have average tap water, you need KNO3 and KH2PO4. You also need a source of trace elements, which can be Greg Watson's CSM+B or it can be a commercial trace mix, such as Flourish. Your big tank will go through commercial trace mixes pretty fast, so CSM+B would be the best idea. Assuming you have about 300 watts of PC quality light with good reflectors, I would start by dosing 2 tsp KNO3 3X per week, 3/4 tsp KH2PO4 3X per week, and 1/2 - 3/4 tsp CSM+B (dosed dry) 3X per week. If you have much lower light than 300 watts, I would cut down to 2X or less per week. If your water has a low GH, or little or no Mg component of the GH I would dose Greg Watsons Barr GH builder too.