Yes that would certianly lead to a sudden spike in nutrient levels as it decays and releases all the nutrients stored in it, back into your water coloum.

Small frequent water changes is a good thing. They will always contribute to lowering your nitrates and other nutrient build up in the water from the tank. However one or two doesnt really do much for you given your current conditions in the tank. Doing a couple of 2 gallon water changes with fresh Salt mixed with R/O water a week for a few weeks should do your tank some real good. Its a slow gradual process and a pain to do but you will likely find the results well worth your while in the end.

There is likely one of your problems, inadequate clean up crew. You seem to have enough Hermits but your seriously lacking on snails. I nassarious is not nearly enough. I would suggest another 9 Nassarious or Cerith snails and 6-10 Banded Triochus/Astrea or better yet Margarita snails. Why so many snails you may ask? Well not all snails are created equal. Some have a tendency to clean the glass and rocks and some have a tendency to clean the sand bed. You need both, especially right now. None of them will do much to eat the Cyno, but they will go a long way in preventing the conditions in your tank that favor Cyno and algae growth in your tank. Clean tanks have very little nutrients in them and therefore minimal algae issues. Your water my be gin clear but that doesnt mean it ain loaded with high nutrient levels.

Removing all of the Cyno will defintiely be a step in the right direction. Removing this while it is in "full bloom" is as effective as removing algae from your fuge when it has grow a lot and gotten think and you tear about half of it out and throw it away. The same pricipal is at work here, your just doing it with Cyno and Hair algae instead of Macro Algae from your fuge. Dont let the Cyno "die off" and "go away" on its own. When it dies off it is realsing all of the stored up nutrients back into the water coloum which will fuel a new bloom in a day or two.

Good! Not a fun way to spend your lunch break, but much better than the option of looking at a faltering tank all day. Keep it up and the hard work will pay off. It just takes a while. Nothing good happens in a SW tank fast.

I was suspecting all along that you had less than optimal water flow in the tank although you never posted (or I over looked it if you did) what the water flow charatristics where in the tank. This is something that will also have a profound effect on Cyno in the tank. If you have adequate water flowing in the tank and no dead spots then this will keep deteris (sp?) suspended in your water coloum (sp?) where your filter can suck it up and trap it in the filter floss or what ever means you are using for mechancial filtration. When you clean the filter which should be often, especially at this point you are removing this crude instead of allowing it to decay and load your tank up with DOC's (Disolved Organic Compounds) such as protiens, Phosphate ect... .This doesnt mean go an add a couple of Maxi Jets pumping 300 gph to your tank. Thats insaine and the wrong kinda water flow to use. High volume in a wide flow patterns does more good for you than high flow concentrated in a narrow stream pattern such as you would get from a typical power head.

Here is an example of what I am talking about. I have a 10 gallon AGA tank with a AC 30 filter and in addition to the 150 gph of water flow this puts out I am using two Koralia Nanos. For a 10 gallon tank that is adequate filtration and the nice wide flow pattern of the Koralia Nanos which move 240 gph each. This equates to a fairly gentle but brisk flow of 630 gph.

Now thats what I am talking about. Bio-Balls in a SW tank often leads to a Nitrate issue. They are great for providing excellent surface area for bacteria that deal with Ammonia and Nitrites but the other edge of this double edged sword is that after they get a build up of film on them it creates a huge "Nitrate Factory". This is why you likely cant get your nitrates down to 10 ppm or less where it needs to be for corals in your tank.

If you have the correct spectrum of bulbs and they are not due for a bulb change..., in your tank, cutting down the photoperiod will get you minimal results. First of all Cyno doesnt require light, its bacteria not algae. Most nucense(sp) alhgae gets plenty of ambient light from its surrounding such as light comming in a window accross the room of the tank or when you trun the lights on in the room so you dont trip over that sneaky ottoman.

It takes more than this to have corals in a tank. Stable water parameters that are not within acceptable ranges in water with high nutrient levels does not make for a suitable enviroment for corals. You started this tank on 25 May 09 if I read the replies right and here it is 23 June 2009. I say this not to be mean but this tank was never ready for corals to begin with. Im not sure it was finished cycling, but with no parameters to look at over the last 4 weeks I cant say for sure. It takes about 28-45 days for a tank to truely cycle and start to settle down a bit. It takes another 4-8 months for the tank to run its course, mature and start to settle down and sabilize. During this 5-6 month period of no corals and in a tank this size no more than one fish you have plenty of time to deal with the various stages your tank will go through as it matures. During this time you will see a diatom bloom that will develop first and go away in a few days, you will start to see a little powdery green algae develop on the glass and the snails will deal with this. You will see some hair algae develop possibly and your clean up crew will easily deal with this in short order. If you have a bout with Cyno it will likely show its ugly sinde at this point. With minimal fish, minimal fish food going in the tank and no other live stock other than a clean up crew this should be a short live battle that you easily win. If you had an adequate clean up crew in the tank to begin with you most likely would have avoided this fun little stage. And finally as your tank began to mature and stabilize you should have started to see some nice growth rates of coralline algae. At this point you would be more than ready for possibly a second tiny fish or some coral additions without upseting the balance of your tank.

But hey thats just my opinion. But that opinion is based off several years of experience and success at this. Yeah, sure you can find someone that will disagree with my opinion, its easy to do. Just look around on forums long enough ro head down to the LFS and find a sales person and they will hook you up with a different version of "the story". But do some research and you will find a lot of merit in the points I am trying to make here in an effort to help you out in the right direction.