I know I am a bit late responding but I have to agree that Biospira won't help with nitrates, if the problem were nitrites or ammonia then it could be useful. I feed my tank every 2-3 days and the tank looks fine, fish are nice and active and everything looks good. How is the flow in your tank? Sometimes increasing flow can help with cyano, between good flow and cutting back on your feeding (your feeding the cyano too due to excess nutrients) the cyano should begin to subside. I have also heard of people keeping their lights out for a couple of days to get rid of it.
On the water thing, the $10 price tag for Catalina Water at PetCo is their normal price, try checking with some other local fish stores to see if they carry it or sell premixed saltwater from RO/DI water. You could also look into buying an RO unit and making your own, this would also eliminate the carrying water all over the place. You can use an RO unit without having it installed if your in an apartment or something. I have mine just sitting on the counter with the drain line in the sink and use a faucet adapter to supply it with.