If a person is having an algae issue, cyano or otherwise, it is not because they used Instant Ocean salt. It's more typically a hardware or husbandry issue.
Instant Ocean does NOT contain Phosphates or Nitrates, that is a completely false statement. If a persons test kit indicates that instant ocean does contain phosphates & nitrates, they probably don't have a quality test kit.
Excess nutrients are what most nuisance algae issues are fueled by, Better maintenance practices will cure outbreaks. Cleaning and adjusting protein skimmer several times per week is helpful & often not being done. Assuming a person has a good protein skimmer and it's adjusted properly, it should need cleaned several times per week.
Increasing water flow can help with preventing localized pockets of nutrients that can trigger cyano. In other words, keeping matter suspended to be trapped by filtering media or removed by skimming prevents pockets of organic matter that will feed algae.
Elevated ORP levels seem to deter cyano. This may be due to aggressive oxidation of organic matter through ozone injection but it works very well.
Using "chemicals" to treat cyano is not sound responsible advise either. Not only do these products kill desirable organisms but they only treat the symptom. If you don't correct what aloud the algae to be there in the first place, it'll be back again. Plus killing the cyano releases the nutrients it had banked in it's tissue, you just re-released what you don't want in your tank! These significantly over priced products are just erythromycin, if you have a situation where you feel you need to kill cyano, you can buy Mardel's Fresh Water Maracyn for a ton cheaper and have the same results, a small pack is like 6 or 7 bucks.
I have to coment on this; A quote from Techguy "I use Kent, do a weekly 20G water change, and only rarely dose Ca. I hated IO!" Here's a little industry secret for you. Instant Ocean and Kent marine Salt are virtually identical. Aquarium Systems & Kent Marine buy the raw materials to make their salt from the same company. Both Aquarium Systems and Kent marine are owned by the same company, Central Pet. Just humorous to me that you bash one and rave the other when they are the same product with a different label.
Instant Ocean does have it's shortcomings for many with reef aquariums but these are easily compensated for with the addition of carbonite, calcium & mag supplements. Instant Ocean is perfectly fine as is for many aquariums, especially fish tanks and non stony coral type "reef" aquariums. I've used instant ocean for over 20 years and have had only 1 time where it had a problem which aquarium systems admitted to there being a problem with that batch. That's a pretty good track record.
Anyway, look else where for algae problem, don't blame the salt...
Joel