I'm setting up my 55 gallon again and I'm wanting the bottom of the tank to be closer to the lights. How deep could I make my substrate? I intend to use oil dri as the substrate, the light is a 4 bulb odyssea t5 ho fixture using two separate ballasts. I want to plant glosso, swords, and various stem plants that I already in other tanks. I want the substrate deep enough for the swords to thrive and the substrate close enough to allow the glosso to thrive. How deep is too deep, and would there be any problems in the long run from having a substrate five to seven inches deep? Thanks for any advice.