I would suppliment your LR
just a little bit. typically you want 1.5-2 times your tank volume. get that in there, then, as electrikat suggested, do a big water change, I'd say about 20%, leave about a week and do another. and pull uut your bio balls slowly during this process (a few each day until they're all gone). The bioballs are doing some filtration so as you remove them you'll want the tank to recooperate the lost bacteria.
Whats happened to your tank is that there hasn't been any real fresh cleaning, so nitrates and extra nutrients have built up, providing a haven for the algaes and cyano
. A little vigourus maintenance over the next couple of weeks with the addition of some more LR
and you should be good to go. I don't see any reason a new cycle would start. (a cycle starts when there is an influx of waste production (fish added or large amounts of die off) without enough biological filtration to handle it. With your current LR
you have plenty of filtration.
another though, you might want to consider picking up a sandbed revitilizer. This is basically a bag of sand dwelling worms, pods
and critters to be sure the sand bed is populated well and moving. you can get some from garf.org and a few other sites. Google is your friend!
Good luck and keep us posted!