[ScubaSteve]

Ok, let's go through causes first. What kind of livestock are you keeping? How much are you feeding? What are your params at? And, are you doing ULNS of some sort. Let's see if we can't kill it at the cause first as it will make the battle easier.

Some cyano, in ULNS especially, can look like dinos, so becareful to not misdiagnose the issue. I had this recently myself. All it took was a small change in my husbandry techniques and they were gone in a little over a week.

There are mixed schools of though on peroxide. Some say it's safe, some not. It works for some but can lead to disaster for others. I use peroxide in my research to kill off organisms in water, so I've seen what it's capable of. Peroxide can create hydroxyl and superoxide radicals which can attack tissue (which is how they kill dinos) but can also be absorbed in to the tissue of corals. When a coral gets too much light the zooxanthellae start to produce these same radicals, so the coral bleaches (or evacuates all the zoox) to protect itself. Adding chemicals into the tank that can produce those radicals could potentially cause the corals to trigger a bleaching event. I'm not saying that this will happen, just saying that if you go this route you need to be careful.

I'd say go for escalation rather than full out nuclear war at the beginning. Let's nail down the cause if we can, and use some of the age-old methods to kill them off. Pull out the magic bullet if all else fails.