I just recently bought a 56 gallon column tank from petsmart. I have a few live plants in there such as cobumba, ludwigia, jungle vines, crypts, and some grass looking plants. I also bought a light fixture to upgrade form the stock lighting which comes with one 6,700k T5 18 watt bulb and one T5 18 watt colormax bulb. I want to upgrade the lighting and I'm looking for the best possible results for my plants. My question is should I just buy another fixture with the same bulbs or should I get another fixture entirely? The fixture I have now just sits right on top of the glass top that came with the tank. Also, my fish are 4 fancy phantom tetras, 6 pristella tetras, 3 lemon tetras, 1 high fin blue ram, 1 yo yo loach, 2 cory cats (the ones that stay small). the dimmensions of my tank. It's 30" W x 18" D x 24" H