Hello I recently got out of saltwater and decided to transform my 40 gallon FOWLR salt tank into a 40 gallon planted. So far I have dual T5's putting out 78 watts, and am using 6500K bulbs. The other fixture is T8 bulbs putting out 34 Watts, and I'm using Zoo Med's Plant growth extreme bulbs in that. All total I have just short of 3 Watts per gallon. Does anyone think I need more or should this light setup be enough to make a lightly planted tank.

It depends on the light requirements of the plants you intend to keep. It also depends on how deep your tank is. If you have a deep 40 gallon tank getting 3 watts/gallon and a shallow 40 gallon tank getting 3 watts/gallon, the deeper tank is getting notably less light. I have a shallow tank getting 3.6 watts/gallon 12 hours/day, plant food once a week, no CO2, and I can get away with keeping *most* plants that require "medium" light.

Depending on the depth of your tank, I'd say you're just shy of the "medium" light requirement, but there are SO many factors that determine whether you can successfully keep plants. I'd say start with a one or two plants each in the "low" and "medium" light requirement ranges and see how they do, then go from there. It sounds like you've got enough light to give it a go.

Z

Well it sounds like you've got enough light for what you want to grow.