I agree with Krazie4Acans. 

For me in this case, rather than re-invent the wheel, I'll refer to two recent forum discussions where excellent advice (hopefully) eliminated the Cyano for good.

http://www.utahreefs.com/forum/forum_posts.asp?TID=82630" rel="nofollow - http://www.utahreefs.com/forum/forum_posts.asp?TID=82630

http://www.utahreefs.com/forum/forum_posts.asp?TID=82539&KW=cyano&PID=624855&title=type-of-algae#624855" rel="nofollow - http://www.utahreefs.com/forum/forum_posts.asp?TID=82539&KW=cyano&PID=624855&title=type-of-algae#624855

Aloha,

Mark  

808-345-1049 call/text anytime for reef advice

Last night, Chuck and I exchanged quite a number of texts and he sent me some tank pics. It was fun to work through it. 

After thinking about it overnight, I thought I might share the things that seemed to me to be contributing to the Cyano. I am extremely analytical, maybe even obsessive-compulsive about details. Analyzing the details is like hunting deer with a powerful rifle rather than a shotgun. I've been solving reef tank issues this way for over 20 years. This makes me very confident but also tends to make my written advice come across as kind of arrogant. In person I'm not so arrogant in person. 

1.   "Tank has been running since January." 

That's a young tank, still growing it's biofiltration. Cyano starts when the bioload exceeds the biofiltration.

 2.  "Tank is [only 13 gal and] is heavily stocked with sps, lps and softies [and] 4 fish." 

In my opinion the tank is not mature enough to be so heavily stocked. Though I always say that fish pollute the water while coral filter the water, coral do create waste and put off a slime that requires processing by the biofiltration. Skimming helps but biofiltration is more powerful than commonly understood. In other words, even where there is a skimmer, a lack of sufficient biofiltration can lead to these kind of problems, because a lot of waste does not get handled by protein skimming.

3.   " ...every other week 5 Gallons water changes religiously." 

Unfortunately, water changes provide nutrients for algae growth. My usual advice when there is a nuisance algae problem is to suspend frequent/large water changes and stick to the standard 10% monthly water changes.

 4.  "Tank was seeded with dead old rock."

As many have discovered, LR has a plethora of animals living right to the core. When they die, it can take up to a year for the pollution, including heavy metals to seep out of the rock as it recovers. Chuck had already started using my best advice, placing a pad of Poly-Bio-Marine's Poly Filter in the system to deal with the pollution coming out of the rock. 

 5.  "No other type of [nuisance] algae but the cyano." There is a small ball of Chaeto and spots of Coralline Algae growing in the tank. My suggestion is to add more Chaeto and even some Caulerpa. Each algae removes specific combinations of pollution. Any algae that is eating pollution competes with the Cyano for nutrients. A young tank without sufficient other biofiltration can benefit from macroalgae growth left in the system for many months or maybe years. That's why Refugiums are so useful. 

6.   Final point. The pics show a 100% Oolitic sand bed with practically nothing in the way of worms and bugs. One of the advantages of larger sand and rubble is its ability to harbor worms and bugs. The setup method described in the Reefkeeping Tips thread linked below suggests using a ~1/2" layer of Oolitic sand with ~1" layer of larger particle sand on top. Bugs and worms do an important job in the biofiltration process. It could really help to add an infusion of those micro-animals by adding some LS and perhaps some LR from a well established, mature reef aquarium.

Hope this helps.

Aloha,

Mark  

Please come back later with an update on what's working.

Aloha