How does Hydrogen Peroxide (H2O2) affect Dinoflagellats?


New member
Hello reefers!

I have decided to start a new thread on this as my other is getting very messy. I have been battling Dinos for some time now (not to sure as I have tthe wrong ID for some time) and I am failing to cover ground. I have tried several methods to erradicate it which include:

-Manual Removal
-Products to kill it
-Carbon Dosing
-Algae Scrubbing
-Lights out
-and the latests and current method is Hydrogen Peroxide.

My questions are:

- How does Hydrogen Peroxide affect Dinoflagellates?
- Does is prevent them from growing?
- Can it beat Dinos back to a desirable population or will it just hold them off until dosing is stopped?
- Is Ultra Violet Sterilization a viable method in beating them?



In Memoriam
The answer is exactly this

the outcome ranges from zero affect to total sustained cure and nothing can be pinpointed to plan for your tank, other than how to dose the peroxide safely regarding the nontarget organisms. post full tank shot

Everybody guesses as to the mechanism of cellular death when exposed to h202. I would suspect actual cell lysis occurs in certain concentrations, and complex free radical devastation inside the metabolic machinery occurs at lower levels, when it does work. sorry its not more exacting than that man, but its worth a shot. We do have several cures with it. UV varies with opinion. if your tank was mine, Id have a pond sterilizer on it yesterday. not an aquarium sterilizer, one meant for a 5K gallon koi pond.
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New member
Thanks Brandon, I have read through your threads about H2O2 dosing and it really got me excited for it!

I have been dosing H2O2 for a week now in conjunction with a 3 day blackout. At the end of the blackout, the water had a haze that turned back into Dino threads once light returned, which got me thinking about UV sterilization. Also this haze has only occured when H2O2 dosing was also being done, and it obliterated some GHA that has some how lasted all this time, which gave me faith in it.

How would you go about peroxide dosing with a UV unit inplace? Wouldn't it decompose the Peroxide before it has a chance to affect cells or will the peroxide have sufficient time to destroy dino? Infact, how long would you suspect peroxide to stay in a system before decomposing? How often have you heard peroxide to be dosed at and still be considered reasonably safe dosage? I have been double dosing (before and after light cycle) for a few days but I am wondering if it would be safe for me to go above double dose?

Currently, its night time here so the best I can do is post any images I have on this SD card. The images are from quite awhile before I did the blackout so they are some of the worser pictures. That mushroom released from its old location (I believe from being smothered by dinos) The dinos are currently alot better but it is getting quite bad again. Also the white balance is completly off on most of them which makes everything look really yellow and are really overexposed. :headwally:

Here is more like what it is like now.

Thanks again for you help!
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New member
The only thing that worked for me was adding a UV sterilizer and doing a complete blackout (blanket covering the sides of the tank to avoid all light from entering) for 3 days. Dinos can sure be a pain but they can be beaten.


New member
The only thing that worked for me was adding a UV sterilizer and doing a complete blackout (blanket covering the sides of the tank to avoid all light from entering) for 3 days. Dinos can sure be a pain but they can be beaten.

This gives me hope, I keep reading about people essentially restarting or completely throwing in the towel to this plague. I hope I don't join either of those two categories...

I use black rubbish back to black mine out, seems to do the trick. I looking online now for a UV sterilizer.


In Memoriam
without a full tank shot I cant give the full info about safety in higher than normal dosing but thats a good start

the full tank shot gives us ideas of nonstated intolerants like the whiskers of a lysmata cleaner poking out from a rock structure or the bulbs of an anemone flowing in the current...we also get an idea of the organic waste loading of the tank, sand bed accumulations, rock structure designs that may be housing lots of organics (whereas knowing at least something about organic loading/export for the tank allows for better high end guessing) etc

some dino tanks look like strains of cyanobacteria as well so I like to talk nutrient loading along with dino discussions, just my opinion, in case my id is wrong. at least it addresses future problems if the dinos can be beaten.

current pictures contrasted with the older ones shows areas of regrowth, overall biomass loss etc.

pretty much all peroxide work is a guesstimate, when i do them I go by feel of the pics and the results are what we collect in the various threads. lots of people are saying dinoxal works better if that helps to know.

for the times we had dino work done successfully, the keeper wasnt dosing a tank full of dinos. they were hand removing the dinos continuously, and dosing to prevent the recurrence, and they might have been running simultaneous UV for a combined assault. I know I would. Some who had it locally just removed and dipped the rocks but yours is more aggressive across substrates, so yes it appears an in-tank treatment is what you will need if you choose to go this route.

people aren't usually willing to do the hardcore repeated manual removal part, and in fact are told not to by those reaching for repeatable actions when battling dinos, so they just settle on inputting peroxide from a general safe dose amnt to see what happens.

There is not one action that produces a repeatable result when battling dinos. they say changing water is bad, yet we see tanks that beat them with nonchemical dedicated removal. We see tanks that could not beat them (DNA) using standard approaches that other tanks easily used to win, Im telling you Dinos are TRICKY and nobody has the answer.

if you want to peroxide dose this bad boy, ill put it up in the thread for a spotlight its considered a heck of a challenge :)

I still give ya these chances:
40% will win, 60% will not win and you will still have dinos
99% chance of accurately dosing the tank without harming non targets, and you must also factor in the current state of stress from all this dosing and recent dino battle work. corals hate instability, but we are rather good about controlling collateral loss so post up full tank shots if you have tried all other methods and are left with just this one. I am not sure how long peroxide hangs around before dissipation...that wasnt needed to get the results we get in the thread so I never pressed for it much. Regarding UV use, you can only under do it. If you arent running a pond sterilizer, its just another shot in the dark and even with a grossly oversized one all you are doing is hedging bets in your favor. nothing is certain with dino invasions.


New member
Ok I will give a full overview of my system.

The system is 11 months old.

-30 Gallon
-1000lph return
-2 1600lph Powerheads
-1cm deep substrate
-2 24w T5HO and 1 18w T8 Actinic


-Temp 27 celcius
-pH. 8.3/4
-Nitrates 0.000 Salifert
-Phosphate 0.00 Salifert
-SG 1.026


-4 Toadstools
-5 Kenya Trees
-2 Mushrooms
-Various Zoas
-2 GSPs*
-Finger Leather

The Xenia and GSP have been in poor condition for a while now, the Xenia has been closed up and not growing since Carbon dosing and the GSP has been consistantly smothered by Dinos.

-2 Clowns
-1 Yellow Tail Damsel
-4 Hermit Crabs

I have took some random shots today of the Dino growth, it seems to have bloomed once again. When it blooms, it always covers the Kenya trees, Finger Leather, one toadstool, Xenia, Most Zoas. Here is a link to a Photobucket Album <div style="width:480px;text-align:right;"><embed width="480" height="360" src="" flashvars="" type="application/x-shockwave-flash" wmode="transparent" /><a href="javascript:void(0);" target="_blank"><img src="" style="border:none;" /></a><a href="" target="_blank"><img src="" style="border:none;" alt="josh40996's Dinos album on Photobucket" /></a></div>



New member
Another quick update, this morning it looked like the Dino bloom was over and had subsided ALOT. However, it didn't last long. I forgot to dose some peroxide and when I returned home it looked like it had bloomed once again...

Water clarity is AMAZING! I am really impressed, not to mention that the Dinos have steared clear of the glass for some odd reason.

The only downside so far is that since the increased dose, one of my mushrooms (my "healthiest one") has really gone downhill and shrunk right down in size. Today, it has released from the rock. I can still see zoa growth so I am not worried.

I have also found a pond uv sterilizer rated for 20,000 litre ponds. I'm hoping that'll suffice. Being a student, I'll have to wait until the 31st before I can purchase it :D


New member
Oops I think I just had another death from the H2O2. I made the stupid mistake of direct dosing 35% peroxide :S I was trying to direct dose a patch next to the xenia and it spread over to them. The rock and Xenia fizzed for around 5 min


In Memoriam
So the old 10x dosing accident zapped ya huh :) xenia is a risk even at 3% but I think you will be okay for the rest

A water change is in order if an od ever happens I'll try to catch up on the thread after work


In Memoriam
I regularly dosea one gallon tank with 5 mils 35 pct as in hundreds of times so I think youw be okay

Xenia is long gone from mine too lol but I don't miss it

Mine is only in system while I clean algae but that's still a brief concentration much higher per gallon so I think you will be okay. How much did you add


New member
I only had 0.5 ml of 35% in a syringe which is what I have been dosing just diluted in some RO/DI. A patch was annoying me so I thought I would just add 0.1 or 0.2 mls on the patch and the rest as usual. I didn't see anything happen so I squirted it all on and then a cloud of bubbles appeared! :D

When I got that frag, it arrived DOA. I placed the rubble it was on in the tank and after a few weeks, a new colony sprouted. Its amazing stuff but I don't think it survived that, its a shame but its been on its way out for some time now, at least it went out in style. :p


New member
Hmm, today was interesting. As the atinics turned on today, I noticed that the water was very hazy, just like it was when I did the 3 day black out. As the actinics came one, the haze grew into tiny strands but then stopped. The haze went and so did the strands. The dinos have not grown back as they normally do with the day/night cycle :D

This "colony" grows amazingly quick (so it seems to me). I started with a 25 polyps colony less than a month ago. I have fragged 5 polyps off of it (they have grown to 8).

One and a half weeks later (actinics)



New member
Just thought that I would do a quick update (no pictures yet)

On Monday 4th November, my 24w JEBO UV Sterilizer arrives. I assemble it and plug it in but it does not light up, I open up the power supply and see that a wire had come loose and I had to re-solder it back on. Close it up and we have power!

That night I covered up the aquarium and turn the light off. For 3 days my skimmer went nuts, on the third night the skimmate collecting jug overflown. It smelt real good...

I turn my light back on after 3 days, as before with all the blackouts, there are some residual patches of Dinos. However, I saw no Dino bloom :O The next day, still no Dino growth, since I hadn't done a WC in 3 weeks, I did one and siphoned out some of the substrate. Today, there is no new Dino growth and in fact, some of the Dinos that remained are now gone! Awesome!

Its amazing, this is the longest I have seen my tank without any problems for a very long time. Touch wood, I have beat Dinoflagellates. :D :D :D


New member
And on another note, so far we only have 3 casualties, zoa frags, a neon green stripped mushroom and a GSP frag. The Xenia is still kicking, it has grown to a little round nub with a tiny polyp forming. The GSP frag had been covered in Dinos for a while and since the lights have been back on, no polyps extension and it has turned white.


New member
Hehe, I am seeing lots of pink calcareous algae growth on the glass and alittle on the rocks.

What is also interesting is that my Nitrates have risen from 0 to 2.5 ppm and Phosphate has risen to 0.03. The water is much clearer and polyp extension has increased dramatically.


New member
Glad things are looking up. I used a multi-pronged attack on mine when the tank was newizh (peroxide, manual removal, blackout, pH elevation, heavy GFO use) and that did the trick for me.