New guy , need advice on lighting hight

The light intensity directly under each AH Supply light, one bulb, will be about 30 micromols of PAR at 24 inches from the bulb. Because those lights are about 35 inches long, you will have two of them, end to end, to cover the whole 6 foot length of the tank. So, you end up with 2 rows of AH supply bulbs over the tank. Under 2 bulbs, the intensity will be about 60 micromols of PAR at 24 inches from the bulbs. That is low medium light. And, that is with the bulbs right at the top of the tank. If you actually raised them to the top of the 15 inch tall hood, they would be about 37 inches from the substrate, 29 inches plus 15 inches minus 5 inches of substrate minus about 2 inches of hood structure, giving you 25 micromols of PAR, which is very low light.

But the tank is 18 inches from front to back, so you might mount the lights about 8-10 inches apart in the hood. That reduces the actual intensity at the substrate a little, but improves the uniformity of lighting, and the shadowing of low plants by high plants. You might have low light as a result, even with the lights at the top of the tank.