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Hydrogen Peroxide vs. cynobacteria (long)
Recently I've been experiementing with hydrogen peroxide as
a non-antibiotic treatment for cynobacteria. I've been looking
through the Krib and the APD archives. From the past discussions
(started by August Eppler), the use of hydrogen peroxide to
combat cynobacteria seems very experimental. So I hope my
anecdotal experience can be helpful to others.
The tank is a new low light set up, 35 gallon, lighted by two 30W
fluorescents. Alkalinity is 2 meq/L. pH is 8.0-8.2. The tank is
not CO2 injected. The non-plant occupants are malaysian trumpet
snails and ghost shrimps. There is no fish. The plants are new
from my main tank, and are a mixed of java ferns, anubias and
assorted stem plants.
Cyno is never a problem in my main tank so I didn't disinfect the
cuttings. So most likely cyno was introduced to the 35 gallon by
the cuttings and it started growing everywhere.
The first thing I tried is to increase the nitrate by dosing PMDD.
I raised the nitrate level to 15ppm, but that did not slow down
the cyno. I looked into erythromycin but decided to reserve it
as a last resort. In the past, I had also successfully light starved
cynobacteria in a fish-only tank, but I didn't want to do it in a
plant tank. So I decided to give hydrogen peroxide a try.
(Interestingly, phosphate was undetectable).
To test out hydrogen peroxide, I applied a little bit of it onto a patch
of cyno using a turkey blaster. Contrary to August Eppler's report
in the Krib, bubbles almost immediately came up from the cyno.
The next day, that patch of cyno lost its slimyness and I assumed it
I decided to try a higher dosage. August Eppler's friend used 2 oz
in a 10 gallon fishless tank, but I was worry about the shrimp and
snail. So I used 4 oz, again spot treat using a turkey blaster.
Most of the cyno looked dead the next day. Unfortunately, so were
many shrimps and snails. In the second day, I reduced the dosage to
2 oz. I also used the turkey blaster to blow away whatever cyno that
was remaining on the plants.
More cyno, shrimps and snails death in the third day. I further reduced
the dosage to 1 oz. In the fourth day, almost all of the cyno
I didn't count the shrimps and snails, but the lost is probably minimal.
There wasn't much snail and shrimp left anyway. It looked like I
have reduced the cyno population to a level that the plants can compete
well, and I stopped the treatment.
The plants took hydrogen peroxide quite well during the treatment.
Everything looked good except some tender new leaves of
Hygrophila polysperma. The new leaves of H. polysperma seemed
to be weaken (not killed) by the hydrogen peroxide.
I also measured ammonia during the treatment. No ammonia was
detected, but this was fishless tank. Therefore, it is inconclusive
on how hydrogen peroxide affect the bacterial filter.
I didn't exterminated the cynobacteria. I can still see tiny bit
of it in the tank but it is not growing. It is not my intention to
exterminate it anyway because inevitablely, cyno will be
re-introduce by new plants. The idea is to reduce it to a level
that higher plant can compete well. Hydrogen peroxide treatment
has achieved this goal for me.
- Hydrogen peroxide is an effective treatment for cynobacteria
with little affect on plants.
- As for the amount used, 4 oz per 35 gallon (minus substrate)
spot treatment is already effective. That's roughly 2 oz per
- There doesn't seem to be an effective and safe dosage level
for snails and shrimps, and possiblely for fish.