# Out of control cyanobacteria and algae, thinking about a blackout.



## Diana (Jan 14, 2010)

Cyano can be killed by a Gram positive antibiotic such as Erythromycin. 
One company (Mardel) packages it as Maracyn (no other word- it is not Maracyn II, Maracyn Plus or other). 
API packages it as EM. 

Do one clean up, the best you can, and clean the filter. 
Dose daily for 5 days. 
Monitor the ammonia, nitrite and nitrate. EM should not cause problems with the beneficial bacteria, but just in case. 
Otherwise it is better not to do water changes while medicating. 
At the end of 5 days do a water change that includes cleaning up all the dead material you can, cleaning out the filter, and add some activated carbon. 

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Black out:
Do the best job you can to clean up, remove whatever algae you can. 
Feed the fish, not extra, just a regular meal. 
Cover the tank to exclude light. A thick, black garbage bag might do it. Not a cheap, thin one, though. Make sure it is not touching any source of heat, and does not interfere with the filter. 
Leave it for several days. NO PEEKING. Plants (including algae) will respond to just a brief flash of light, and keep on trying to grow. 
After 5 days you can uncover it. Feed the fish a normal meal (don't overload them with food). 
Do the best clean up you can, including the filter. 

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You can also squirt stuff at the algae when you do a water change. 
Hydrogen Peroxide or Excel are the most commonly used products. 
Figure out what is the maximum you should put in your tank. 
Put that much into an eye dropper or syringe (no needle). Squirt this into the thickest masses of algae until you have used it all. 
Next week, hit another area. 

Dying algae (from whatever treatment) can overload the filter with dead matter, or cause an ammonia spike. While these methods are fairly quick, you should monitor the conditions (ammonia, nitrite, nitrate) and the filter as the algae dies.


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## lee739 (Oct 12, 2014)

How big is the tank, and how are you doing water changes?
For me a big part of the time taken is assembling gear and packing away - can you increase the change to 50-60% weekly, you might find it helps swing the balance to your favour....


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## GrumpyGills (Jun 20, 2014)

It is a 40b. I will do a bigger water change this week and then black out for a few days. If that doesn't work I will try the antibiotics.

If I am sealing up the tank, how do I ensure oxygen gets into the water? I don't have an airstone.


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## lee739 (Oct 12, 2014)

GrumpyGills said:


> It is a 40b. I will do a bigger water change this week and then black out for a few days. If that doesn't work I will try the antibiotics.
> 
> If I am sealing up the tank, how do I ensure oxygen gets into the water? I don't have an airstone.


If your filter isn't some sort of trickle arrangement, I'd add an airstone....


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## GrumpyGills (Jun 20, 2014)

It is a HOB which does agitate the water a bit.


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## lee739 (Oct 12, 2014)

If well enough sealed, I'd be concerned that the air above the water may become hypoxic, then agitation will do nothing - at least an airstone would bring fresh air into the water column and above the water....


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## GrumpyGills (Jun 20, 2014)

Alright I'll see if I can find a cheap airstone and pump. Again, just trying to keep this as simple as possible.


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## BanzaiJoe (Dec 23, 2014)

I used a combination of a modest dose of 3% peroxide and a partial blackout. 

Just left the tank lights off for 3 days and put a car shade along one side and the top to reduce the majority of ambient light hitting the tank. I dosed 30ml of peroxide into my 46 gallon tank on two consecutive days. The following morning I was surprised how much cleaner the tank was. All the cyano was gone.

In my case I have a mix of community fish and Amano shrimp. All seemed un-fazed.
BTW, I did still lightly feed the fish during this period.


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## Chazerr (Feb 25, 2015)

I've used neoplex (By Seachem) to whip out a bad case of cyano in my 75 planted. It killed some of my weak panda corydora, but the cyano has been gone for good.


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## Raymond S. (Dec 29, 2012)

Don't take the word "seal" to serious. No tape etc, just put the bag over the tank.
Good plant growth is the best defense against algae, especially Cyno.
So are you using any ferts in there ? Erythromycin kills Java Fern BTW.
As was stated before Excel or Peroxide at the same time as the blackout is good.
If you use Peroxide like Excel you can just dose it at the same time you do the black out @ 1 ml per gallon if you have shrimp and 2 ml per gallon if not.
Peroxide kills Riccia F.
A picture of the whole tank always helps diagnose problems in algae problems also.


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## thump421 (Nov 29, 2014)

Out of curiosity does peroxide have a negative effect in hc? I've heard spot dosing with it can melt it but not sure on the method stated above.


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## Kathyy (Feb 22, 2010)

Peroxide killed its close relative HG aka HM aka MM in my tank, if you use peroxide don't squirt it directly on HC although I didn't as the plants lost didn't have any algae on them. It also killed Riccia and Najas. If you have moss I wonder if any have trouble with it as well. There is at least one thread somewhere on what plants are affected by H2O2 here.

Get the antibiotic, it won't kill plants, didn't kill any fish or snails. Didn't hurt my filter bacteria either. Or maybe lift the HC and remove during H2O2 treatment.

If you haven't resolved the problem maybe cyano won't come back but another algae will take its place. I got rid of cyano but green water moved right in as my tank was low in nitrogen. 

If you black out the tank then make sure it is a good long one and the tank is really black. Put your covering over your eyes to see if you can see through at all. I had to use several layers of blankets to get a good black out. Plants will be bothered by it, some will be just fine but light hogs like Myrio get pretty weak.


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## Monster Fish (Mar 15, 2011)

A 6 day blackout killed off all the cyanobacteria in my tank. I just did a large water change before the blackout, removed all lighting, covered the tank with a black trash bag, waited 6 days, took off the bag, and did a large water change. The blackout killed my floaters but those can be replaced. My crypts, buces, and hygros shrugged it off. The blackout also killed most of the spirogyra and staghorn growing on my plants.


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