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[APD] The cure for Green Dust Algae (Akistrodesmus) infestations

I orgnially identified this species found in our aquaria a few
years ago(GSA, BGA, Staghorn as well). 

This species is likely Akistrodesmus falcatus (Corda)
The films we typically see are almost pure cultures of
zoospores(asexual) and are motile.

You will note upon cleaning the glass, they seem to grow back in
30-90 minutes. This is not **new growth**, the alga's zoospores
simply swim around after being scrubbed off, find a nice lit
clean surface and begin to grow(the glass seems to be the
favorite place). It's rarely on plants or wood etc.  

The issue is that folks do not allow this asexual spore to
complete it's life cycle. Then after this stage of the life
cycle is completed, it's no longer a problem for us. 

This is not a vegetative adult algae stage. Nutrient limitation
cannot be done to get rid of it or increase to stop growth
without damaging plant health a great deal. Many have tried and
failed miserbly for many months. Similar to green water. I'm not
entirely sure *what induces* this alga, but after the tank runs
it's course, it does not appear to ever come back with typical
high nutruients levels or EI dosing etc. Intense light seems to
be part of it's induction.

The cure is deceptively simple:
Leave it the heck alone.
Do nothing, let it grow, do not wipe the glass, after about
10-20 days, the film will produce patchy thicker patterns and
parts of the film will fall off. At this point you can go in and
clean it off. 

I've done this is 9 tanks now(100% success rate) and several
other folks have reported success and no return of the alga
after a long bout.

I'm not entirely sure everyone will have this experience, but it
does seem fair consistent using several tanks and other folk's
reports as well as using basic life history and ecological
approaches to cure it.

It is particularly presistent and a nusiance for many folks
growing plants.

So this is yet another non snake oil, low impact method that can
be used to cure the tank of certain species of algae.

You'll note over the years I've shown that: BGA=> NO3
related(easy to cure with blackouts/NO3 dosing), BBA=> CO2
related, GW=> NH4 related, Staghorn=> urea/GW related, Green
spot algae=> CO2/low PO4 related, GDA=> life history stage

Each species that causes us issues have particular traits and
they widely vary. If you want to deal with control of a certain
species, you ought to get to know that species well. 

But hobbyists books are terrible at elucidating anything
worthwhile, highly speculative at best, web sites tend to be
even worse and support as many myths and bring new ones up all
the time.
I still get clowns claiming PO4 limitation will cure BBA and
excess PO4 causes BBA. That's after over 10 years of telling
folks there's no causual effect between either of them. 
The best book I've seen to date was Baensch Atlas vol 2. 
They got the genus correct for BGA, and CO2=> BBA.

I attack these myths barbarically often times, but it's because
they are myths and I know they are because I've done a fair
amount of background test and observations on the algae as well
as taxonomy, culture, repeatable test, methods to cure it that
do not cost $$$. Myths are not people, they are just bad ideas. 

Tom Barr


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