NANFA-- Fw: AES Splash 12-21-00

B.G. Granier (
Fri, 22 Dec 2000 12:13:16 -0600

----- Original Message -----
From: Aquatic Eco-Systems <>
To: <>
Sent: Thursday, December 21, 2000 9:35 AM
Subject: AES Splash 12-21-00

A Publication for Aquatic Eco-Systems Customers
Volume I, Issue 4

Welcome to the fourth edition of Splash. We hope you will find our
newsletter both informative and entertaining. If you have any
suggestions or contributions, please contact us at


De-icing Lakes and Ponds

Most of us are aware that aeration systems are primarily required in
summer, when the oxygen consumption rate is the highest and
stratification is most severe. In some lakes, winter fish kills are
also quite common.

When ice covers a lake, the oxygen transfer from the atmosphere is
greatly diminished and, if there is a significant accumulation of snow
on top of the ice, the photosynthetic oxygen production can be virtually
eliminated. If the ice cover persists long enough and the oxygen
consumption underneath the ice is great enough, there will be a fish
kill. The winter fish kill dynamic is based upon the duration of ice
cover, the amount and duration of snow cover, the depth, the rate of
oxygen consumption beneath the ice, and the rate and quality of ground
water flow through the lake. Clean lakes, that is those that a have a
low trophic state index, may not require winter aeration.

During the summer, thermal stratification occurs when warmer water
floats above cooler, heavier water. Near freezing, the situation is
reversed. As water approaches the freezing point, it expands and floats
on top of warmer water. We can see this with floating ice.

The oxygen consumption that takes place in a lake can be called
"chemical reactions." Since the rate of chemical reactions are directly
related to temperature, the winter aeration system needs to be only
about 20 percent of the size of a summer aeration system, as the rate of
oxygen consumption has slowed way down.

If it is acceptable to have an open hole in the ice, the simplest way to
prevent a winter fish kill is to keep a small area ice-free, either by
using air or an electric, propeller-driven de-icer. The electric
de-icer may work best at the shoreline, perhaps mounted on a dock, and
the air-powered systems seem to be preferred where longer distances are
involved. When the air compressor is mounted on the shore, the air line
is buried below the frost line into the lake and directed to the area
that is to remain ice-free. Caution must be taken due to the hazards of
open water in the winter, where people may be on the ice. Also, be
careful not to open too large a hole in the ice because too much of the
lake's heat can be lost.


The following question appeared in a physics degree exam at the
University of Copenhagen:

"Describe how to determine the height of a skyscraper with a barometer."

One student replied:

Tie a long piece of string to the neck of the barometer, then lower the
barometer from the roof of the skyscraper to the ground. The length of
the string, plus the length of the barometer will equal the height of
the building."

This highly original answer so incensed the examiner that the student
was failed immediately. The student appealed on the grounds that his
answer was indisputably correct, and the university appointed an
independent arbiter to decide the case.

The arbiter judged that the answer was indeed correct, but did not
display any noticeable knowledge of physics. To resolve the problem it
was decided to call the student in and allow him six minutes in which to
provide a verbal answer that showed at least a minimal familiarity with
the basic principles of physics.

For five minutes the student sat in silence, forehead creased in
thought. The arbiter reminded him that time was running out, to which
the student replied that he had several extremely relevant answers, but
couldn't make up his mind which to use. On being advised to hurry up
the student replied as follows:

"First, you could take the barometer up to the roof of the skyscraper,
drop it over the edge, and measure the time it takes to reach the
ground. The height of the building can then be worked out from the
formula H = 0.5g x t squared. But bad luck on the barometer.

"Or, if the sun is shining you could measure the height of the
barometer, then set it on end and measure the length of its shadow.
Measure the length of the skyscraper's shadow, and thereafter it is a
simple matter of proportional arithmetic to work out the height of the

"But if you wanted to be highly scientific about it, you could tie a
short piece of string to the barometer and swing it like a pendulum,
first at ground level and then on the roof of the skyscraper. The
height is worked out by the difference in the gravitational restoring
force T = 2 pi sq. root (l / g).

"Or if the skyscraper has an outside emergency staircase, it would be
easier to walk up it and mark off the height of the skyscraper in
barometer lengths, then add them up.

"If you merely wanted to be boring and orthodox about it, of course, you
could use the barometer to measure the air pressure on the roof of the
skyscraper and on the ground, and convert the difference in millibars
into feet to give the height of the building.

"But since we are constantly being exhorted to exercise independence of
mind and apply scientific methods, undoubtedly the best way would be to
knock on the janitor's door and say to him, 'If you would like a nice
new barometer, I will give you this one if you tell me the height of
this skyscraper'."

> The student was Niels Bohr, the only Dane to win the Nobel Prize for


We are greatly in need of information about your experiences
on our website. Will you take a few moments and answer a small
six-question survey? We would greatly appreciate it. Please click
on the link below.



12V Diaphragm Compresser Was $178.00 Now $165.00
12V Diaphragm Compresser, twin head Was $375.00 Now $330.00

We offer two excellent values in American-made oil-less 12 volt
compressors. These very popular compressors are great for mobile use,
emergencies, and for solar-power applications. They are specially
designed for aquaculture, providing high volume at low pressure (10 psi

Power Filters

Power filter, Skilter 250 gph Was $35.15 Now $30.00
Power filter, Skilter 400 gph Was $46.30 Now $40.00

This power filter is great for saltwater systems. It provides chemical,
mechanical and biological filtration and features a builtin protein
skimmer to remove organics. The large filter housing allows ample room
for additional media. BioMatrix filter pads are included.

Mag Drive

Mag Drive Pump, 350 gph Was $48.95 Now $40.00

These robust, epoxy-sealed, low head centrifugal pumps are magnetically
driven and they can be completely submerged! They work well in both
fresh and saltwater, above and below the water.


Binocular microscope Was $579.00 Now $500.00

This binocular microscope offers high performance and durability at an
excellent price. Features 10X wide field

Ph Tester

Oakton Waterproof pH tester Was $55.00 Now $49.50

Never again lose your pH instrument due to water damage. These pH
Testers are completely waterproof to a depth of 3 ft. If dropped in the
water, they will float, making them perfect for field work, hydroponics,
aquaculture applications, or anywhere frequent pH testing is required.
Six month warranty.

Koi Net

Koi Sock Net Was $49.98 Now $39.98

This is a must have net for Koi keepers. With an 11 in. diameter opening
and a 42 in. sock length, this net can handle the largest of Koi. Great
for moving Koi to prevent self inflicted wounds.

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