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[APD] RE: Oedogonium & black-outs

Tom wrote:
> [Steve wrote]
> I've been trying to discover if there is a black-out protocol
> that might
> be effective against Oedogonium.
> =============
> Well you can kill it easy enough, but you are still left with
> the nagging question, why do you have it to begin with?

(see my question at the end of the post)

Background for Dr Armstrong's reference: We are discussing control of
Oedogonium epiphytic filamentous algae infecting a 5 yr old 75 gal
aquarium with 250 watts MH lighting, moderate fish load, CO2 injection 1
bubble/sec, regular water changes with CA, K, NO3, Mg & trace
supplementation. P is provided primarily via fish food/wastes and from
soil in pots.

There is an abundance of CO2, nitrate and other minerals. No shortages
there. The substrate is contained only within pots in this tank and is
over 5 years old in all cases. Oedogonium has been present in small
amounts for quite some time in this tank but what has apparently
triggered it is the increase in nitrate levels in the last 3 months.
Other tanks which are showing tremendous growth improvement with
increased CO2 & nitrate do not have this problem however the other tank
that has been exposed to Oedogonium has a lot of Rainbows in it and they
might be eating it. The other difference between the tanks is that the
problem tank has a lot of slow growing plants in it. I have a huge mass
of H polysperma in this tank which grows very rapidly and I crop it
regularly for sale. The slow growing plants cannot throw out leaves fast
enough to keep ahead of the spread of Oedogonium. The new growth on the
H polysperma does not appear to have any colonization by Oedogonium
(yet). I do not have a microscope nor access to a microscope so I cannot
determine if there are any small colonies on the H poly. There are a lot
of assorted Tetras and Sword tails in this tank; not exactly the best
algae grazers. I might be able to get a hold of some Mollies which are
said to be good grazers.

So I submit that the reason I have it is not due to a lack of nutrient
dosing. Perhaps with a different population of fish or a bigger
assortment of fast growing plants, this tank would not have a problem.
Slow growing plants do not seem able to out compete filament algae when
you start to push the nutrients. I think the green filament algae groups
(Oedogonium, Cladophora, Spirogyra) really gets going well when you
provide "ideal" hydroponic growing conditions for aquatic plants.

I do attempt to prevent infestation of my new aquariums by the use of
the bleach protocol (ala Krombholz). Spirogyra seems to spread from tank
to tank very easily however it is the easiest to combat using the
black-out protocol that we discussed several months ago. Strangely,
Oedogonium does not seem to spread from tank to tank although I cannot
be certain that there aren't small colonies of it in some of the tanks.
Once it takes over, it can be a real problem to get rid of. I had a bad
case of Oedogonium several years ago and I resorted to tearing the tank
down and bleaching all the plants and equipment.

Oedogonium does have motile zoospores however the motile zoospores do
not seem to survive on equipment if you dry it off or rinse it off. That
is educated guess work.

I'm fairly cautious with my "clean" tanks and I rinse the water change
Python out with a bleach solution before changing the water in those
tanks. That can be a pain in the but because ideally, you want to do a
major water change every few weeks.

According to Paul K, in private emails, he has said that he has tried
very long blackouts with Oedogonium (6 months) and the algae did not
die. To me, that suggests that the algae had formed non-motile zygotes
(combination of a non-motile gamete egg and motile gamete sperm) which
can be dormant for extended periods. Oedogonium also produce asexual
motile mitospores which attach and form new filaments. These are not
dormant or persistent spores.

For a better understanding of the 3 methods of reproduction by
Oedogonium see <http://www.ulala.org/Bio203/Biol203.html> and

Other relevant information can be found at:
<http://www.ucmp.berkeley.edu/greenalgae/chlorophyceae.html> and

BTW, the Armstrong reference is part of a fascinating online text:
by Joseph E Armstrong, a botany professor at the Illinois State
University. I will CC him on this email and hope he doesn't mind the
publicity. :-) <http://www.bio.ilstu.edu/armstrong/armstr.htm>

So finally, my question:

Tom, have you ever used the black-out protocol to try to kill
Oedogonium? Do you think it will be successful in knocking down the
thick colonies that are covering virtually all the leaves of my slow
growing plants in the problem tank?

I covered the tank completely on Wednesday evening with heavy blankets
and added air injection to keep the oxygen levels up for the fish.

Steve Pushak
Steve's Aquatic Plant Resource Page

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