red tide in marine tanks

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Nov 27, 2005
I am writing this article for whoever has a mysterious algae that they just can’t seem to get rid of. I have been battling Dinoflagellates for almost 4 weeks now and have just discovered in the last couple of days what I actually have.
Dinoflagellates is commonly mistaken for an algae when in fact its not an algae at all but a photosynthetic bacteria that is more commonly associated with red tides and very rare in aquariums. After searching the internet numerous times and coming up with nothing I thought that it might be a good idea to share my experience with you so that if you are ever unlucky enough to get Dinoflagellates at least you will have a chance at beating it. Before I go into any detail here is a pic of Dinoflagellates in all its glory, notice how the strands which are protruding into the water column have small air bubbles attached to them:

For this article I will refer to Dinoflagellates as an algae.

My problems seem to have started when I moved from a T5 luminaire over to a 150w halide and within 2 days my tank was covered in a brown slimy substance which I assumed was red slime algae as prior to installing the halide I had small patches of red slime algae (cyano) so I thought that with the intensity and light spectrum change the slime algae had bloomed and in a day or so would have burnt itself out. How wrong I was. Here are a couple of pics of my tank after about a week:

At the end of my first week I lost my first fish a mandarin. I added a PO4 reactor at the beginning of the algae bloom and that didn’t seem to make a difference so after week of no change and the loss of my manderin I took an aggressive approach at blasting the rocks with a power head daily, small parts of the algae would rise to the surface so I would scoop them out with a net, I would do 10%-15% water changes and vacuum the gravel twice weekly but my efforts where in vain as the next day it would be back, you wouldn’t even think I’d touched it, it would return that quickly. This went on well into the second week. At the end of my second week I lost my second fish which was a cow fish. I tested all my parameters which came back excellent apart from my KH which read 5.8dkh so I went out and bought a buffer and buffered my KH up to 11dkh, my PO4 was 0ppm, my nitrates where less than .5ppm everything which causes algae was within range so next I turned to my lights which where on for 9hrs a day so I reduced them to 5hrs a day (1hr actinics 4hrs halide) throughout all this I continued with water changes and blasting the rocks with the powerhead and still no change. I began to notice that my urchin was beginning to lose its spines and I would also find upturned snails which at first I thought it was the hermit crabs so I would turn them back over, my corals where beginning to suffer at this point I had already lost 2 fish and now my corals, something had to be done. At the beginning of week 3 I was really getting fed up so I considered using a chemical, an oxidizer but was talked out of it. Half way into my 3rd week I lost my third fish my regal tang which really sickened me at this point I was ready to jack it in and go back to tropicals and then I came across an article on Dinoflagellates which outlined some of the symptoms to look out for:

From The Reef Aquarium Vol 1, Delbeek and Sprung pg 270
"Dinoflagellates occasionally bloom in reef aquaria, and they can be toxic to invertebrates and fish. They form nearly colourless to rust brown gelatinous mats and films that trap oxygen bubbles. They can also be present in large numbers in the water column and on the surface of the water during a bloom. They coat bare surfaces so quickly that it is futile to siphon them off."

The Reef Aquarium Vol 1, pg 326-327
"...the appearance of a mysterious slimy material coating both living and non-living surfaces in the aquarium. This material has the consistency of nasal mucus and it can be dark brown, light tan or nearly colourless. It usually develops as a light coating but soon entraps air and forms long strings that float up into the water."

"... blooms are toxic to aquarium inhabitants. Herbivorous snails may roll over, stop eating and die. Tangs that eat the dinoflagellates may stop feeding and starve to death. Sea urchins that eat them may loose their spines and die."

Quite a few of these hit home and I realised that I had it totally wrong it wasn’t Red slime algae but Dinoflagellates after some further research I wasn’t that far off with the treatment of this plague so I added some activated carbon to my canister filter and I’m pleased to say that the algae is on the retreat, I’m not out of the woods yet but things are looking a lot better than they did 3 ½ weeks ago:

My recommended treatment is as follows:

01. Turn off lights for a full 24hrs followed by a reduced lighting period of 5hrs
02. Add a PO4 Reactor or at the very least RowaPhos to a canister filter
03. Elevate any parameters which aren’t at recommended levels
04. Add a good quality activated carbon to a canister filter
05. Increase skimming efficiency
06. Increase water flow
07. Cut feeding to at least every other day and feed small amounts

How I got this algae is still a bit of a mystery as its extremely rare in aquariums, one possible cause is live rock as around the time I added the halides I also purchased a kilo of live rock which could have possibly contained spores either from the ocean where it was collected or from another source possibly the LFS as they had a similar outbreak a while ago, the algae could have lay dormant and my tank provided the ideal breeding ground, I may never know the true cause of this outbreak but one thing I do know is that I never want to experience it again as it can devastate a tank in matter of days.

Dinoflagellates can be very toxic to both aquatic life and humans so please if anybody thinks they have this algae make sure you wash your hands preferably with an antibiotic hand wash after coming into contact with your aquarium.

I would like to thank maxilaria who helped me a lot through this nightmare, thanks max for you patience.
A little back ground on tank set up etc.
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