[sihaya]

What's the deal with this stuff? I've never known anything to actually die without metal halide lighting. But whenever I get this stuff, if I turn off the MH for just a day or two, it all dies. ?!?

I'd rather not get it ever (especially since it does seem toxic), but I don't know what exactly causes it. Could I possibly have too much light on my tank? I'm not having nuisance algae problems (except for that evil caulerpa). So I don't really get what's going on here. (I run carbon and Seachem phosphate remover too.)

[leebca]

How have you identified them as dinoflagellates? Why do you say it seems toxic? How much light and what kinds and how many hours do you have on your tank? What is the "evil caulerpa?" Have you checked the phosphate concentration? the nitrate? the silica?

Hard to answer unless there is more background.

[sihaya]

Ok, first, I've only had one big bloom of them (if that's indeed what it was). I suppose I determined they were dinoflagellates by visual appearance, its behavior, and by process of elimination. I say it was toxic because my corals "freaked out" when I got it, then stop freaking out after each time I manually removed it (then freaked out again when it grew back each day). During this big bloom, I did water changes and manually removed the stuff every 3 days for about 2 weeks. It happened right after I lost my sand bed (do to the tank leaking and having to be replaced). So you're right, I could be assuming causation where there's only a correlation.

The one time I checked the phosphates and nitrates during the bloom they were both undetectable. But I know that doesn't mean anything. The dino (or whatever it is) could have been taking it up fast enough to deplete it from the water.

In the end, I was able to control it (and ultimately get rid of it altogether), but keeping my MH light off for 3 days. However, again, this could be a coincidence since I had been taking other measures to control it too. Ever since then, if I even see a little of it starting, I turn off the MH for a day or two and it goes away again.

Still... I noticed while I was battling it that it grew visiably while the MH was on (at an alarming pace), and didn't grow while the MH was off. This is why I started to wonder if it actually needed the intense lighting to grow.

Hope that makes sense...

[leebca]

An astute observation about the phosphate and nitrate concentrations and their relationship to the growth. You'd be surprised how many aquarists assume if they are ND that it means they aren't there. They forget that having the invasive microbe could be the cause of low or ND readings.

Although some dinoflagellate (zooxanthellae) growths of these unicellular algae live symbiotically with corals, there are many that live independently in marine (and freshwater) systems. They are in fact why many corals need intense lighting -- so these algae can provide the coral with food and survive. They do produce toxins. Without actual visual confirmation under a microscope, you might assume the growths are dinoflagellate by characteristics. It would still be a good idea to get them seen under a microscope, if you can.

They can be almost totally autotrophic (needing light to live) to all the way on the heterotrophic end of the scale (needing organics to live) and then there are those that are parasitic.

Getting back to your case, depending upon the species involved IF they are dinoflagellates, the ways to kill them would also harm most of your display marine life. The use of UV and Ozone (the former is the best) will control numbers in suspension, but not eliminate them. The UV is best set at the energy level and flow to kill protozoan.

Those that may cover rocks, substrate and aquarium walls are best controlled through snails. The combo of hungry snails in sufficient quantity and the UV will and have kept dinoflagellates in the 'they're there but not noticeable' category.

[Reefland]

Does an elevated pH stop their growth, say around 8.4? Seems I have read/heard this before.

[leebca]

I have not heard of that. Maybe it is true for some specific dinos? Most marine dinoflagellates have a wide 'confort' range to marine conditions, as far as I know. But that doesn't mean that operating at the edge of what is good for a reef system won't encourage or discourage their growth.