How do I get rid of it?
The best way to get to battle cyano would be diligent tank maintenance. A combination of regular water changes, great filtration, not over feeding or over stocking, manual removal and good water flow. Regular water changes will help remove organics and lower nitrate and phosphate levels which are large fueling sources. Regular testing will help you keep your level in check but, keep in mind that test kits can only measure inorganic phosphorus. If any phosphates show in your testing, this means there is a higher amount of organic phosphates. Anything above 0.03ppm should be lowered asap. I feel at this point I should also add that using tap water may be adding to the problem. Testing your tap water would be advised. Some tap water contains phosphates and nitrates in which case RO/DI water would be necessary for top offs and salt mixing. Other things that may help are adding more waterflow to your tank. Cyano will thrive in low flow stagnant areas. Manual removal will help as well. Siphoning the cyano from your sand/gravel and rocks with airline tubing will help remove bulk amounts of cyano. Be sure to remove any cyano that you wipe from the sides of the tank as well. Feed less. Just because the fish swim to the top like spoiled dogs begging doesn't mean they need fed every time you walk past the tank. Actually, it's good practice to skip a day of feeding. Many aquarists feed every other day. Commercially prepared foods contain a lot of phosphates as well. A homemade frozen blender mush* is a good alternative frozen food. This is a mix of fresh seafood and vitamins thats not full of preservatives. If feeding daily, feed small amounts so there isn't a lot of excess food laying around. If feeding frozen foods, thaw the food in some tank water and drain before feeding. Care should also be taken when feeding inverts/corals. It's easy to overfeed so be wary of adding too much. Few animals will feed on cyano and only as a last resort for food. Some hermits may pick at it and nerite snails are said to eat it but the only true consumer is strombus sp. Introducing macros that will compete for the nutrients will help as well. Lastly, there are several chemical products on the market that can be used to control cyano. These can be a mixed blessing. While it may control and/or eliminate your cyanobacteria, these fixes are usually temporary. Cyano being so adaptable, unless you change the conditions in your tank that is causing the problem in the first place, it will often adjust itself to the new chemicals and reappear over time.
In closing, cyanobacteria is not the end of the world. Algaes of all types are to be expected in a new system. When the tank first cycles, there is an over abundance of nutrient and as a result much larger than needed bacterial populations. Once the nutrient load is reduced and fish added (or inverts), the bacteria start to die off. The nutrient bound up in these bacteria then become a great source of algae fuel. Once the tank reaches a more static level (waste in/waste out), these algaes subside naturally for the most part albeit unsightly for the short term if the conditions/removal suggestions are followed. Limit nutrients through regular water changing, careful feeding, limiting use of supplements, proper lighting, adequate filtration, circulation and aeration, and the addition of macro algaes. If you do have an outbreak of cyanobacteria, look for the fuel source. Things like lack of competing algaes, overabundance of chemicals and foods, as well as stagnant, low oxygenated water are pretty easy fixes and are better for the long term health of your tank.