No the extra bacteria depletes the oxygen. Expect some water cloudiness. Having your skimmer on should ensure oxygen depletion isn't a problem, but make sure your skimmer is tuned up to actually remove the bacteria else your just shuffling organics around but keeping them in the tank (and they will eventually , annoyingly, reappear). Also beware a bouncing pH.
Your phosphates are quite high so the rowaphos is a good idea though if you've got a lot of phosphate bound to carbonate material in your tank it might take a while for anything positive to happen (and you'll go thro' a lot of rowaphos). Your blaming your cyano on nitrates you don't know the level, changes in amounts of, and old lights? SOunds like clutching at some pretty thin straws to me. What's your pH day and night, kH? How much stuff are you getting skimmed out. Any other algae problems? To get to the bottom of this I would really need to know the details of your setup (I guess they're on here somewhere), stock. How much flow do you have, how much substrate , what % covered by live rock, any sticking, concreting of said sediment. There are quite a lot of things to investigate, think about here. I'm not saying you're doing the wrong thing, but reducing an unknown level of nitrates w/ sugar is not how I'd start.
Also bear in mind your tank is still quite young, you should perhaps expect a few things like this while it stabilises.
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