Hi Lynn ...
Reefworm is right on the mark. Even after the tank cycles organisms on the rock continue to die off and release organics into the water column. The tank maturization process can take awhile until you are left with the critters that are adapted to their new captive enviornment.
Looks like the room this tank is in is pretty well lit with natural sunlight. Looks like you might have your work cut out for you but it shouldn't be impossible. Hopefully one day you can open the blinds on your beautiful room! J/K
I would close the blinds or cover the tank til the algae was under control. If you cover the tank make sure that it can still breath! A little light is probably necessary but natural sunlight can wreck havok on even the most established tanks. Light control is a temporary fix until the underlying issues can be addressed.
I would remove all the algae possible, without getting too crazy at this point and disturbing the rocks. I didn't notice if you had a DSB but if you stir that up now you are going to have more organics than you know what to do with.
I would also make sure that you have a efficient skimmer for your anticipated bioload. That probably means buying one that is rated for a larger aquarium. Also ensure that you have plenty of flow inside of the tank. If you don't have an efficient system you are going to fight with algae for a long, long, time.
After the cycle is complete I would focus on getting all the excess nutrients out of the tank so the photoperiod can be increased and you can take your sheets off of the tank.
Several large water changes with RO/DI water should be the place to start. Always ... always... use RO/DI and test it to make sure that it is pure before adding it to your tank. The same goes for anything you put into the aquarium. It can be hard enough without fighting ourselves.
Like I said earlier there will more than likley be continued die-off and subsequent organics released even after the cycle. Nomaly things will stabalize themselves over time but it is slow and can take months.
You can counteract this to a degree by continuing with RO/DI water changes and running a canister filter for two days each week with carbon and phosphate absorber. At least for the first month or so while the organic release is at it's greatest. Make sure you dont run it longer that 48 hrs or the compounds will leach back into the aquarium. It will cost money but it will reduce the intensity of your algae blooms and you might even be able to add livestock a little faster. Still go slow though.
Start with snails... Astrea, Turbo's, and Cerith's and a small photoperiod. You should be afraid that your snails are going to starve to death from lack of algae before increasing the amount of light.
As time passes and you can increase the photoperiod I would add a small fish or two that you can be content with for the next few months and keep the feedings light. Week by week you could possibly add a smaller coral. If you planned on some lower light requiring organisms, they could be some of the first things added. Remember the tank is already releasing nutrients itself. If you add hungry fish and other items that require you to add alot food. You will be asking for algae. Get to a point were your can be content with the tank for the most part bare and then slow down even more. Let the tank stablize from your additons of the past few weeks. After your tank shows that it can deal with the current bioload for a couple of weeks with turning into a green mat then continue. But always give it a rest to insure that you have not gone too far too fast.
Remember it is a balancing act with nutrients. Algae is just your barometer.
Looks like it going to be a wonderful tank!
Good Luck