Do the WPG guidelines tend to break down and be obsolete with small tanks like a 10g? I've heard that high-light plants you need upwards of 10-12wpg in a 10g, whereas on a larger tank you would only need half of that. Could someone offer an explanation as to why this is true? I'm asking because I'd like to set up my 10g to be mostly open with just Dwarf Baby Tears or Glossotigma and some driftwood. I have a desk lamp that I've been using on that tank for a while and it gives me 27 watts at 6500k, but the light doesnt spread very well because the bulbs are small and close together. So I was thinking of purchasing another desk lamp and having them side by side to illuminate the entire tank with roughly 6 wpg. Would this be sufficient for a foreground-plant tank?