It usually takes a combination of control measures to gain control of dinos. The most important measure is to siphon them out, clean the sand bed and scrub them off the rocks. Running GAC to reduce the dinos toxins and run GFO to control nitrate. Lights out per Randy's article is a good control aid to reduce their growth and set them back, but without the other control measures will not be effect. Increasing pH is a last straw IMHO.
Problem Dinoflagellates and pH
http://reefkeeping.com/issues/2006-11/rhf/index.php
From Randy's article:
How to Treat Problem Dinoflagellates
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Here's a series of actions besides raising pH that may help aquarists to deal with problem dinoflagellates.
1. Reduce available nutrients in the water. These include nitrate and especially phosphate. In a severe case, the concerns with driving phosphate too low may be minor compared to the dinoflagellates (and their toxins). In addition to the usual ways of reducing nutrients (skimming, growing macroalgae, deep sand beds, etc.), aquarists should consider very aggressive use of granular ferric oxide (GFO). Putting a larger than normally recommended amount into a canister filter or reactor, and changing it every few days, may help. Don't bother to measure the phosphate level, because the goal is to have it well below normally detectable levels (say, 0.02 ppm).
2. Reduce the photoperiod to four hours per day. This may help to keep the dinoflagellates under control, but by itself will not usually eradicate them.
3. Use more than normal amounts of activated carbon, and possibly ozone, to deal with toxins that the dinoflagellates may be releasing. This may allow snails and other organisms to survive while the dinoflagellates are still at nuisance levels.
4. Manually siphon out as much of the mass of dinoflagellates as possible.
Daily removal would be preferable to keep populations at a reduced level.
How to Treat Problem Dinoflagellates: Elevated pH
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In order to treat problem dinoflagellates with elevated pH, I'd recommend keeping the pH at 8.4 to 8.5 until they are gone. The pH can be as high as 8.6 without causing too much stress on anything else. The process may take weeks. In desperation (i.e. if nothing else works), allow the pH to go even higher.
pH is best raised by adding calcium hydroxide, either as limewater (kalkwasser; calcium hydroxide or "lime" dissolved in freshwater), or as a lime slurry. Bear in mind that aeration will tend to lower the pH, so if maintaining high pH is difficult, reducing aeration may help a bit. pH naturally drops at night, so be sure to measure pH in the early morning as well as later in the day.
As a general guideline, adding the equivalent of 1.25% of the tank's volume in saturated limewater will raise the pH by about 0.66 pH units. That increase may be more than desired all at once, but that volume, or more, spread out over the course of a day may be necessary to maintain high pH.
If you are limited by low evaporation and cannot add enough limewater, use a slurry of lime. For example, 1-2 level teaspoons of calcium hydroxide can be made into a slurry by mixing with one cup of RO/DI (reverse osmosis/deionized) water (not tank water). Stir it up and dump it into a high flow area away from delicate organisms. Adding one level teaspoon of solid lime this way into a 100-gallon aquarium will raise its pH by about 0.3 pH units. This process may need to be repeated several times a day to keep the pH high.
Don't worry about raising calcium or alkalinity with this method. The higher pH will accelerate calcification by organisms and abiotic precipitation. Beware that you may eventually clog pumps, impellers and intakes this way, and you might get white precipitates on surfaces (that is usually okay for a short term treatment and does not usually harm corals).
at the beginning i thought it was cyano, i tried leaving my lights off for two days to see if it would help. it seemed like it did but as soon as i turned them on again, the algae came back. ive read that reducing the lighting time will not help. what can i do to eradicate this?
