Panel Discussion Notes - CORRECTIONS SOUGHT PLEASE!

[Erik Olson <erik@thekrib.com>]

What's the name of that guy from Maryland Aquatic Nurseries?
Technical corrections also sought where applicable!

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AGA Convention
Panel Discussion 5-November 2000

One of my favorite parts of aquarium conventions are the impromptu
freeform discussions that occur over the breaks between talks, lunch,
or late at night.  Thankfully, the recent AGA convention featured an
ORGANIZED freeform discussion, moderated by a panel of conventions
speakers Karen Randall, Paul Krombholz, Neil Frank, David Lass and
Charlene Nash, plus special guest George Booth.  For an hour over
breakfast, we enjoyed spirited banter on three aquatic gardening
topics.


CYANOBACTERIA AND OTHER ALGAE

Earle Hamilton has three large tanks, two 300-gallon aquaria and a 220
gallon aquarium, kept right next to each other and with similar
conditions, lighting, etc.  Two of these tanks are very clean but one
gets plagues of cyanobacteria (blue-green algae).  Maracyn
(erithromyacin) is an effective temporary cure, but is very expensive
($25 for 100 tablet was quoted).  Earl has found that an alternative
to this is hydrogen peroxide; it is certainly a lot cheaper.

George notes that algae is natural in a tank --- but when it covers
everything in the tank, it's a problem.  David wonders if the tank is
overfed.  Karen added that the appearance of Cyanophyta is a signal of
nutrient imbalance, and it's best to find the root of the problem
(i.e. the nature of the imbalance).  She also concurs that the algae
is naturally present in particular sites, for instance the waterfall
in a paludarium, or the overflow skimmer.

Cyanobacteria may produce certain toxins, Paul expounds.  Snails do
not eat it under normal circumstances.  But if the light level is
decreases, the algae seems unable to produce the toxin, and in his
experience, snails are able to eat it!  Also, running the water
through a U/V sterilizer makes this algae more "palatable".  Could the
algae be secreting something into the water?

****That Maryland Nursery Guy*** has never seen cyanophyta, green
water and "string" algae co-existing in the same tank or pond.  He
sees phases where new ponds first undergo a case of green water, which
then seems to collapse as string algae takes over.  This is also is
seen naturally in streams --- does the movement of the water help the
nutrients get to the algae?  Karen wonders if it's Allelopathy.  Paul
suggests that the string algae provides a lot of surface area for
rotifers and other critters to colonize.  These small creatures feed
off the unicellular green algae.

Dorothy Reimer has had string algae plagues cured by throwing in some
tetras with "orange and black fins".  The group is curious about
exactly which tetras these were, because they are not normally known
for their algae-eating prowess.

GLOSSOSTIGMA

Glossostigma elatinoides (also known as "that Amano Plant" or "that
impossible-to-grow plant" by your note-taker) is a short carpet plant.
It needs high light and CO2 to grow, says ***That Maryland Nursery
Guy***, but is very easy to grow emersed!  Paul and Karen suggest
growing a bit emersed in a jar on the windowsill, just in case your
rare and expensive sample does not fare well in the tank at first.
Karen muses that some of the trouble we encounter growing it in the US
may stem from a tendency to overcrowd the tank with taller plants,
shading the foreground carpet, while the Amano "style" sometimes
consists of a tank with only Glossostigma and some rocks.  

Neil, who has visited with Amano in Japan, adds that Glossostigma is
not the high-maintanence plant in those tanks; it's actually all the
fast-growing stem plants which require constant pruning by the
minions.  Neil has tried Glossostigma himself, grown in pots, and it
has never developed the large leaves seen in the pictures.  They
produce very shallow roots, and thus must be getting their nutrients
from the water column.  The best tank of Glossostigma he's seen in
this country has it growing in Flourite!  Perhaps the Flourite is
supplying a small but constant amount of iron and other micronutrients
to the plant.

In an excellent example of why your note-taker loves group
discussions, Michael Rubin and Steve Dixon chime in with somewhat
contrary information to the above!  Glossostigma, for folks in the Bay
area, does well in soft water, likes high nitrates, produces 2-1/2"
long roots, grows very fast ("it's a screamer" they say), and will
actually grow into shaded areas.  Another person pipes in with reports
of it growing well in hard water (5 degrees GH).  The group attempts
to rationalize the differences: maybe shade is OK if the bulk of the
plant mass extends into the main well-lit area of the aquarium.  And 5
degrees GH isn't hard water to many.


HEATING CABLES AND SUBSTRATE

George, who has been using Dupla heating cables on his aquariums for
eight years (See TAG ***) begins this discussion by conceding heating
cables are clearly not a necessity, based on the successes of the
panel at the front of the room.  He cites several benefits of the
cables, such as increased metabolism of substrate processes, and
micro-circulation of nutrients between the substrate and water column.
Questions are raised about how much value there is in the
micro-circulation vs. microcirculation *AND* heat vs. heat alone.
Cables, say George, provide spot-sources of heat and encourage
convection (movement of water through the substrate).  Even sources of
heat, such as a heating pad, tend to favor conduction (where the water
stays in place).  Finally, George notes that for him, cables do *not*
help at all for short-term plant growth, but rather contribute to
long-term stability.  His tanks without cables have always "slowed
down" after a year or two, while the cable-based aquaria have been
stable for over five years.

Neil wonders if the effectiveness is dependent of the particular
plants kept.  Plants with extensive root systems, such as Echinodorus,
are able to pump water down to the roots and improve circulation,
while small-rooted stem plants provide no such benefit and might do
better with substrate heating.  Another possibility is the density of
planting.  Perhaps a tank with plants (and this roots) covering every
inch of gravel do not benefit from cable heating very much.

Karen also beleives that the degree of benefit depends on the home
environment.  For instance, it may be more effective in a home that is
air-conditioned as opposed to an 80-degree fishroom.  Neil's home
falls into this latter category; Any excess heat in the substrate for
any length of time would surely cook the tank.  He supplies heat to
the bottom of the tanks by stacking them three-high.  The lower tanks
provide bottom heat for the tanks above them.  There is a report of
some hobbyists in sweltering Taiwan, turning their heating cables on
for one hour per day!

The discussion mutates into substrate temperature in general... One
person reports their discus tank's substrate is cold when they poke
around with their fingers.  Karen suggests they insulate the bottom
with styrofoam. 

Could the style of planting in pots be used to improve the temperature
of the roots?  Neil keeps his plants potted and sitting above the tank
bottom, so the pot is effectively bathed in the circulating tank
water.  Dorothy, however, keeps her pots submerged in plain gravel,
and relies on styrofoam insulation to keep the substrate warm.

***That Maryland Guy*** asks if some plants actually prefer cooler
roots... presumably, this is closer to how things are in nature,
right?

Which is appropriate for the substrate, aerobic or anaerobic?  Neil
thinks that ideally there is a micro-aerobic zone around the roots,
but anaerobic areas around this to allow for reduction processes that
make iron available to the plants.  Paul says this is visible through
the bottom glass as different colors away from or near the roots.  The
terrestrial potted plant folks have figured this out, as they repot
their plants when they become root-bound.

Perhaps heating cables counteract this effect, by making the entire
soil aerobic.  But one could also argue that substrate heating cables
also allow the nutrients from the added fertilizer to circulate
through the roots, so the anaerobic areas may not be necessary.