Genetics has recently moved and has not had as much time since he is still unpacking.....etc. I have seen him on a few times since the move.
The primary pupose for dosing sugar is to reduce you nitrate and phosphate levels. Genetics has stated that using sugar will tend to turn your corals brown. It appears you are over-dosing sugar since you are seeing bacterial blooms. Once your nitrate level drops to zero, you need to decrease the amount of sugar you dose to 1/2 of the recommended rate, which you are way above. He has recently been recommending that you switch from sugar to using glucose which does not seem to turn your corals brown if it is color you are after.
As far as your algae type pest goes:
There are a lot of hobbyists in your same position. Reducing your nitrate and phosphate levels to a zero reading will help in getting rid of many type of algae pests. IME, reducing nitrate and phosphate levels too low can kill or cause problems for many types of coral. Running GAC & GFO will all help in reducing the growth of these type of pests. In many cases they will not eradicate the pest. Vodka dosing will help reduce the nitrate and phosphate levels also, but will not necessarily eradicate the pest either.
IMHO, if you are faced with an algal type pest problem, it is best to implement an algae pest control program strategy:
1) Wet skimming with a good quality skimmer. Clean your skimmer cup at least once per week.
2) Reduce your nitrates and phosphates to a zero reading using the hobby grade test kits. See Randy's articles regarding this:
Phosphate and the Reef Aquarium
http://reefkeeping.com/issues/2006-09/rhf/index.php
Nitrate in the Reef Aquarium
http://www.advancedaquarist.com/issues/august2003/chem.htm
3) Proper lighting. I find that the higher wavelength bulbs are less conducive to algae growth. I now run 20,000 K bulbs from using 10,000 K bulbs.
4) Proper day length is a good thing also. I would not run your lights for more than 12 hrs total. Keep in mind that light entering from a window nearby is added to this figure.
5) Running GAC is a good practice in my book. It will help reduce the total dissolved organic carbons in your tank water and this is a food source.
6) Proper 30% per month total water changes will help export the DOC as well as some of the pests in the water column. It will help maintain the micro-nutrients as well.
7) Physical removal of the pest by hand, scrubbing and siphoning is important as well. If the amount of pest in your aquarium is overwhelming, perhaps dealing with one section at a time is a better idea.
8) Proper water circulation in your tank to prevent dead zones. When dealing with cyanobacteria pests increasing the flow where it grows seems to help.
9) Use RODI water for all top-off, salt mixing, additive mixes... etc.
10) Dosing iron may have benefits for macro-algae, but if you are experiencing algae pest problems than I would stop dosing it as it can add to the problem in many cases.
11) If you are dosing other supplements such as vitamins, amino acids, or others that contain a mix of supplements other than the basic alk., calcium and magnesium, I would stop these until you gain control of your pest. This includes many of the store bought products with unknown ingredients. Dosing Vodka or sugar to reduce your nitrates and phosphates would be an exception in my opinion.
12)
Proper feeding habits. This can be the number one problem when trying to reduce your nitrate and phosphate levels. Use low phosphate fish foods.
13) IMHO, lighted refugiums may be a problem when trying to deal with an algae type pest problem. They are wonderful when it comes to reducing nitrates and phosphates. However, the light over most refugiums is conducive to the microalgae type pests. If the refugium becomes infested with a microalgae pest, I would clean it throughly of all pests as best as possible, remove the macro and turn off the lights until you gain control of your pest. Re-using the same macroalgae later may serve as a source for re-infestation of your pest.
14) There are other items that can be added to this list if others care too share and some of the items listed may be disputed.
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