Hey man,
I got the same tank. Don't give up and don't sweat dinos. It's just a stage. I had them and it's nothing to do with a sand bed. Blacks out will help if they get bad. Here is what worked like a champ to beat them back for me, and they've never come back:
(1) Green killing machined. Works. Fits in the back of you tank, looks fine. Run it until the dinos are gone and then a while longer. Seriously works. Really well. I ran mine for about two months or so. Don't run it now.
24 Watt, for aquariums up to 100 gallons. Power head helps keep aquarium water crystal clear, kills algae, and pathogens.
www.petco.com
(2) Add some corals! Get some softies, lps, whatever. They'll start growing and dinos wont.
(3) Live phyto. Dose it every night and continue to dose it after the UV is out. Get some copepods too. Lot's of little critters to help increase diversity and eat up stuff on micro level i think helps.
(4) Consider a CPR hang on refugium. I put one on and it's nice. if anything like dino's grow--they grow in there and who cares/!
I had dinos last fall and now and i just feed my tank and dose All for Reef and that's about it. I feed pretty heavy twice a day, but do run a skimmer and refugium.
p.s.. i don't touch my sand bed. And yeah my nitrates, and phosphates, etc., are don't show up a API test.. I think it's all coral food. I have macro algae and maybe that helps too--but really just get some stuff growing in there i think is the key.
This is the tank now, after dealing with dinos just a few months ago: