cynobacteria nightmare


Premium Member
Cyanobacteria require food to grow. They might be consuming the nitrogen and phosphorus from the water column as quickly as it's produced. I'd look into nutrient control to solve this issue. A phosphate reactor often helps.


Premium Member
How much food is going into the system, and how much PhosBan is being used? Could you post a description of the setup?
Perhaps these threads and articles will help:

Cyanobacteria thread - problems with trying to control this pest

Blue green algae in aquariums (Cyanobacteria)

Effects of UV and visible light on cyanobacteria at the cellular level

Nitrogen Control in Cyanobacteria

Nutrient control of algal growth in estuarine
waters. Nutrient limitation and the importance of
nitrogen requirements and nitrogen storage among
phytoplankton and species of macroalgae


This is a quote from Boomer regarding controlling cyano:

"Some added thoughts from over the years from many

The only known fish to eat Cyano is Amblygobius stethophthalmus and it needs to be the real one not its close relative that is often Mis-ID with it.

A 2- 3 month scheme

1. Water changes. 25% weekly.

2. Bare bottom refugium only for cheato nutrient export and not for critters.

3. Siphon, sump, refugium, etc. every week during water change and clean all filter you have.

4. Blow off all the Cyano and settled stuff you can so it can be siphoned off.

5. Clean out skimmer and cup every week.

6. Carbon, 1 cup per 50 gallons / 2 wks. Try to use ROX

7. GFO -HC , change every month.

8. Purigen, every month

9. Soak frozen food in RO/DI and discard water before use. This is especially true for brine shrimp. Matter of fact I use to pour off the water, and then fill it back up, to repeat it until there was only whole brine shrimp in the container.

10. Read what is in the food and look for things low in phosphates.

11. Keep the pH in the very low 8's or very high 7's, as Cyano will out compete other algae's in higher pH water.

12. The # 1 limiting nutrient for Cyano is N, not P based on studies in various microbiology texts.

13. During these water changes and blowing stuff off and siphoning it up run a Diatom filter with a second cake of PAC (Powdered activated carbon)."

14. Increase water flow where Cyano are growing, as they do not like high currents.

15. Shutting of all lights, almost total darkness for 48 hr. every few days.

Last resort is Chemi-Clean by Boyd.

99.9 % of the time if nothing eats it and it looks like yours it is Cyano.
Chemical defense of a marine cyanobacterial bloom

From this article:

"A popular Guam beach experienced a temporary closure in May 1994 due to the simultaneous occurrence of a blue-green algal bloom and a massive die-off of juvenile rabbitfishes (Siganus argenteus (Quoy and Gaimard) and Siganus spinus (Linnaeus). The microbial assemblage was composed primarily of the marine cyanobacterium Schizothrix calcicola (Ag.) Gomont with sparsely distributed strands of Lyngbya majuscula Gomont. Palatability of the crude organic extract of this mixed cyanobacterial assemblage was evaluated in feeding assays using the parrotfish Scarus schlegeli (Bleeker) and the sea urchin Echinometra mathaei (Blainville) in outdoor tanks on Guam. Bioassay-guided fractionation resulted in the isolation of ypaoamide, a new broadly-acting feeding deterrent compound. At natural concentrations, ypaoamide deters feeding by juvenile rabbitfishes (S. spinus and S. argenteus), the parrotfish S. schlegeli, and the sea urchin E. mathaei. We propose that the production of deterrent secondary metabolites by this benthic cyanobacterial assemblage and other similar microbial assemblages facilitates the formation of cyanobacterial blooms on coral reefs surrounding Guam."


New member
2. The # 1 limiting nutrient for Cyano is N, not P based on studies in various microbiology texts.

my No3=0 and i have been running sulphur reactor


Premium Member
Did you try to increase flow? But you will still need to limit its food somehow. I would recommend giving Bulk Reef Supply high capacity GFO a try. It worked wonders for me.


Premium Member
I haven't heard of an animal that will eat cyanobacteria reliably, although some people get lucky with individual animals. I don't think Purigen will be useful.


New member
One more article:

I'm just recovering from Cyano. I didn't want to but had to go with the last resort -- Chemi-Clean. All of the Cyano were gone after 48 hrs but a lot of my SPS have been affected and started bleaching big time.

Anyway, my SPS are recovering now, but did lose a cap and a bird's nest (both small). I have upgraded my skimmer and trying to skim out all the remaining chemi-clean as well as doing 15% water change every 5 days.

Chemi-clean is really strong. I think half the dosage might have still gotten rid of the cyano and might have less negative effects on the SPS.

I've learned my lesson.


New member
Has anyone tried bacteria dosing to get rid of cyano? Or used it in conjunction with vodka dosing? I've ALWAYS had a few spots of cyano in my tank, and they grew when I did vodka dosing alone. When I started zeo, and eventually switched to Microbacter7 additions WITH the vodka, the cyano slowly disappeared, and I fortunately haven't seen any in a month or so now that I think about it. I guess it took 2 months of carbon+bacteria dosing to get it to go away.
<a href=showthread.php?s=&postid=15433315#post15433315 target=_blank>Originally posted</a> by chercm
2. The # 1 limiting nutrient for Cyano is N, not P based on studies in various microbiology texts.

my No3=0 and i have been running sulphur reactor

The studies I have read have been made where the phosphate levels are extremely low like those found in the natural reef systems. At these very low levels then phosphate is not a limiting factor. In our reef systems, phosphate is quite high, even in the so called low nutrient systems.

Many cyano bacteria are capable of deriving the N needs from nitrogen in the air also, so limiting N can be next to impossible. Still reducing your nitrate levels to as low as possible is very effective along with reducing your phosphate levels as low as possible.

Reducing your dissolved organic matter in your water column is very important. Good skimming practices, increased water changes and running other types of filers that will help remove the organic matter will all help. Running GAC and replacing it properly falls into this catagory.


Premium Member
I have zero nitrates and 0.03 or less P04 and i've had a couple bouts with very stubborn cyno, even when i have nutrients so low chaeto just slowly dies off. Plus it even grows on closed loop outflows with tons of flow. I siphoned for days, just keeps coming. I've resorted to chemiclean both times, got rid of it in 48hrs. Used as directed, and I had no affect that i noted to SPS nor magnifica anemone. I measured my total water volume as close as possible, and i added aeration. My opinion is that some cyno strains are just too tough not to use the antibacterial like chemi or other.