[APD] RE: why algae will not grow

["Thomas Barr" <tcbiii at earthlink_net>]

> On Apr 1, 2005 4:55 PM, David Aiken <daiken at iprimus_com.au> wrote: 
> > I'd suspect that the process interrupted is actually nothing more than
> > nutrition and that the algae effectively starves as a result of being
> > out-competed for food. What else could it be?

>  But it can't be that -- there is always food available. In fact, there
is 
> more food available now than there was when I had algae growing. 
>  Liz

Liz is correct.
The issue is one of inducement.
Chemicals signal new growth, these might be variations in CO2 for BBA, NH4
for green water and staghorn and maybe other species, build up of organic
matter and high light, low PO4 etc.

Remove these variations for a few weeks, and there is no new growth of
algae, there is nothing to signal the spores and adult algae to keep
growing.

When conditions change, algae generally respond by producing spores and new
growth.
Which alga has a better chance of survival? A smaller young alga or a fully
mature adult alga?
Removing the adults and cleaning them off and then correcting the
conditions and providing a stable place for the plant's needs will beat
back any algae.
Spores need NH4 to get going in many species of algae. 

Healthy plants = very low NH4.

This is true in non CO2 and CO2 enriched tanks.
Plants that are stressed by low CO2 temporarily(CO2 variation) will leak
photosynthate, N and other compounds and also not grow.
This also reduces the amount of NH4 removed from the tank and helps when
combined with low CO2 when the plants are adapted to high CO2.

Low O2 levels rather than high O2 levels might also be a signal. There is
some correlation there.
Plants take longer to get their machiery up and working at full speed. They
have much more biomass and transport distances, diffusion issues.

If it were merely high O2 levels, then adding pure O2 would address the
algae, but when I added pure O2, this did not occur. 

Regards, 
Tom Barr

www.BarrReport.com 
Plant Fest 2K5 in Florida July 8-15(FW and then the Marine version)! Swim
with plecos loose in the wild, Everglades aquatic plant nursery tour, trip
to Tampa Public aquarium presentation at Tampa's aquarium society.



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