|
|
 |
Virtually all of the living organisms listed in the Flinn
Scientific Catalog/Reference Manual can be kept in the classroom
for prolonged periods with minimal effort and expense. We
frequently get calls from science teachers wondering if, and
how, this culture or that animal or plant can be kept alive
and healthy. We felt that a handy, basic reference guide would
be a useful and welcome addition. Following are
some general and specific culture tips, methods and media.
This information covers immediate requirements plus techniques
you and your students can use to maintain cultures for weeks,
months or indefinitely.
These methods carry with them the potential
for long–term projects and experiments
and the invaluable experience of learning
what other living things need to survive.
If for any reason you require more detailed
information, please consult the Book
Section of the Flinn Scientific Catalog/Reference Manual under the heading "Culturing
and Care".
Bacteria
Prior to receiving bacterial or fungal
cultures it is helpful to be aware of
the requirements of the individual species.
Each species has specific conditions
necessary for optimal growth. Refer
to the Bacterial Cultures table in the
Live Material section of the Flinn Scientific Catalog/Reference Manual for incubation
temperatures and recommended media for
each culture. Always keep culture tubes
sealed with caps or foam plugs. Plugging
the tubes will prevent cross–contamination
of cultures and inhibit dehydration
of the medium. Although the cultures
listed in this catalog are considered
to be non–pathogenic, always practice
aseptic laboratory techniques.
Bacterial cultures will need to be sub–cultured to fresh media
every two to three weeks to ensure a thriving culture. New
cultures require approximately 24 to 48 hours for full development
of colonies and for development of pigmentation in pigmented
species. Refrigeration will retard growth rates, allowing
you more time to work with cultures, and will also provide
a means of longer term storage of cultures.
Fungi
Fungal cultures usually require different media than bacteria.
Generally, these contain additional carbohydrates and are
slightly acidic. Refer to the Fungal Cultures table in the
Live Material section for specific media and incubation temperatures
for each culture. Fungal cultures may take a few days longer
to grow than bacterial cultures—between three to seven
days.
Maintaining a pure culture is your main goal when subculturing
bacteria or fungi. It is essential to avoid all contaminants.
When higher than ambient temperatures are required, cultures
must be maintained in an incubator (or laboratory oven capable
of being regulated at a low enough temperature). Culture dishes
should be incubated upside down, this will prevent excessive
accumulation of moisture from diluting or flooding the surface
of the medium. As a means of preventing the medium in dishes
from drying and cracking, and of maintaining proper humidity,
a small container of water can be kept filled in the incubator.
It is not recommended that students randomly culture bacteria
or fungi from biological sources (oral swabs, coughing, spitting,
etc.). The potential for culturing dangerous concentrations
of pathogenic forms is too great. As a wise precaution, culture
dishes should be taped shut immediately following inoculation.
For disposal, cultures should be incinerated, autoclaved,
or immersed in, and flooded with, a disinfectant solution.
Lysol® type disinfectants or a dilute chlorine
bleach solution are acceptable.
Upon receiving, loosen caps and aerate culture with a clean
pipet. Caps should remain loosely in place to prevent contamination,
yet permit free air exchange. Cultures should receive diffuse
light at a temperature of approximately 21 °C. Depending
on the species, the temperature range can vary from 10 °C
to 28 °C. Refer to Table I in this section for recommended
media and any special lighting or temperature needs.
Culture algae in an appropriately sized flask or culture dish,
depending on the amount of algae you wish to grow. Under the
correct lighting and temperature conditions, algae will thrive.
Use cool white fluorescent tubes for your lighting needs.
Two 48–inch, 40–watt bulbs provide enough light for most cultures.
New algae cultures should have a 16–hour light period alternated
with an 8–hour dark period. After 10 days of growth, reduce
light intensity and use a 12–hour light, 12–hour dark cycle.
Subculture to fresh media every six to eight weeks.
Table I: Algal Culture Requirements
Algal Culture |
Temperature
Range |
Lighting |
Recommended Media |
Cyanobacteria
Gloeocapsa |
18 °C to 21 °C |
Moderate to Low |
B.M.M., P.S.W. |
| Oscillatoria |
18 °C to 21 °C |
Moderate to Low |
B.M.M., P.S.W., Knop's Soln. |
| Anabaena |
18 °C to 21 °C |
Moderate to Low |
B.M.M., P.S.W. |
| Nostoc |
18 °C to 21 °C |
Moderate to Low |
B.M.M., P.S.W. |
Chrysophyta
Diatoms |
18 °C to 21 °C |
Moderate to High |
P.S.W. w/sodium metasilicate |
Green Algae
Chlamydomonas |
18 °C to 21 °C |
Moderate to High |
B.M.M., P.S.W. |
| Chlorella |
18 °C to 21 °C |
Moderate to High |
B.M.M., P.S.W. |
| Desmids |
18 °C to 21 °C |
Moderate to High |
P.S.W. |
| Hydrodictyon |
18 °C to 21 °C |
Moderate |
B.M.M. |
| Oedogonium |
18 °C to 21 °C |
Moderate to High |
B.M.M., Knop's Soln. |
| Spirogyra |
5 °C to 15 °C |
Moderate to High |
P.S.W. w/out CaCO3 |
| Ulothrix |
15 °C to 18 °C |
Moderate |
P.S.W., B.M.M. |
| Volvox |
20 °C to 24 °C |
Moderate to High |
B.M.M., Knop's Soln. |
Euglenophyta
Euglena |
21 °C to 25 °C |
Moderate |
P.S.W. w/pea cotyledon |
| B.M.M. = Bristol´s Modified
Medium P.S.W. = Pringsheim´s Soil Water |
Bristol's Modified Medium
Make six stock solutions, each with one of the following salts
dissolved in 400 milliliters of water:
10 g sodium nitrate (NaNO3)
1 g calcium chloride (CaCl2 · 2H2O)
3 g magnesium sulfate (MgSO4 · 7H2O)
3 g potassium phosphate dibasic (K2HPO4)
7 g potassium phosphate monobasic (KH2PO4)
1 g sodium chloride (NaCl)
Take 10 mL of each stock solution and add to 900 mL of distilled
water. Next add one drop of 1% ferric chloride solution, 40
mL of Pringsheim's soil-water extract and autoclave. This
will give you a total volume of one liter of medium.
Pringsheim's Soil Water
Select a rich garden soil which has not been recently fertilized.
Add 300 g of the soil to a gallon jar. Fill three–fourths
full with distilled water then add one gram of calcium carbonate
(CaCO3). Plug or cap jar loosely and steam for
one hour per day on each of three consecutive days.
To culture Spirogyra, do not add calcium carbonate.
To culture Euglena add one-fourth of a pea cotyledon
before steaming. This will enhance growth. To culture diatoms,
add 10—30 mg of sodium metasilicate (Na2SiO3
· 9H2O) to every liter of media.
Knop's Solution
Dissolve each of the following four salts in one liter of
distilled water:
1 g potassium nitrate (KNO3)
1 g magnesium sulfate (MgSO4)
1 g potassium phosphate dibasic (K2HPO4)
3 g calcium nitrate (Ca(NO3)2)
For immediate use, add five liters of distilled water to the
original stock solution. This 1% solution may need to be shaken
before use to mix undissolved salts. Pour solution into containers
and autoclave.
Euglena Medium
Prepare by mixing and boiling 20 wheat grains, 15 rice grains
and 5 mL of skim milk in 500 mL of spring water. Boil for
five minutes. Let the mixture stand overnight and then add
Euglena. Keep in a well-lit area but out of direct
sunlight. Overheating will kill Euglena. Subculture
every month.
Protozoans
Upon receiving, loosen cap and aerate culture with a clean
pipet. Protozoans should be kept in diffuse light or darkness
at temperatures from 18 °C to 22 °C. Refer to Table
II in this section for recommended media and any special lighting
or temperature needs.
Culture protozoans in small (3 ½"
to 4 ½")
sterilized culture dishes with approximately one inch of medium.
Culture dishes may be stacked or lightly covered to limit
evaporation and contamination. Replace evaporated water with
distilled, spring or pond water. Do not use tap water unless
it is allowed to sit for several days. The pH of the culture
must be kept at seven (neutral) or slightly alkaline. Subculture
protozoans every month or when the culture appears overgrown.
Chalkley's Medium
Prepare by combining the following salts with one liter of
water:
0.1 g sodium chloride (NaCl)
0.006 g calcium chloride (CaCl2)
0.004 g potassium chloride (KCl)
Pour Chalkley's medium into culture dish. Add four (for amoebae),
or eight (for ciliates), boiled rice or wheat grains to each
culture dish. Let bacteria grow for 24 to 48 hours. Add a
few milliliters of a Chilomonas culture (or other small
protozoan) to the medium.
Hay-Rice Medium
Prepare by autoclaving or boiling some spring, pond, or aged
tap water. Next add two grains of rice and three small pieces
of Timothy hay, which have been previously boiled, (see note
below) to each culture dish.
Wheat Medium
Prepare by autoclaving or boiling four grains of wheat for
each culture dish. For ciliates use eight grains. Allow the
medium to cool for 24 hours. Pour into a shallow culture dish.
Once a month add four or eight grains of wheat to each culture
dish.
Note: Media made by soaking or heating fresh or dried organic
(usually plant) material in water are known as "infusions".
As a general rule, approximately seven grams of organic material
(wheat seed, rice, oat flakes, hay, etc.) per liter of water
is sufficient. To pre-treat the organic material of choice
it should be placed in boiling water for one to two minutes,
removed, and maintained under sterile conditions. After the
pre-treated material is added to culture dishes the resulting
medium should be allowed to age 24 to 48 hours for the development
of bacteria. The aged medium is then ready to be inoculated.
Table II: Protozoan Culture Media
| Protozoan Culture |
Lighting |
Recommended Media |
Sarcodines
Amoeba proteus |
Low |
Chalkley´s, Hay–Rice |
| Pelomyxa carolinensis |
Low |
Hay–Rice Med. w/Paramecium |
| Mastigophorans |
|
See Algae culture, Table I |
Ciliates
Blepharisma |
Low |
Hay–Rice Med., Wheat Med. |
| Didinium |
Low |
Concentrated Paramecium |
| Paramecium caudatum |
Moderate to Low |
Chalkley´s, Hay–Rice, Wheat |
| Paramecium multimicronucleatum |
Moderate to Low |
Chalkley´s, Hay–Rice, Wheat |
| Spirostomum |
Low |
Hay–Rice, Chalkley´s |
| Stentor |
Moderate |
Hay–Rice, Wheat |
| Vorticella |
Low |
Wheat, Chalkley´s |
Hydra
Upon receiving, loosen cap and aerate culture with a clean
pipet. Hydra should be kept in dim light at a temperature
of 21 °C. Too much light will permit algal growth, which
is detrimental to the hydras. Culture Hydra in a small
aquarium or a large culture dish containing filtered spring
or pond water. Do not use tap or deionized water.
Hydra are extremely difficult to culture for a
long period of time. They feed on live food, usually Daphnia
or brine shrimp. Feed Hydra once a day. Allow several
animals for each Hydra as the culture grows. Uneaten
food must be removed each day or it will foul the water. The
easiest way is to decant off the majority of the water and
replace it with fresh spring or pond water. Even well maintained
hydra cultures go through a period of depression caused by
incorrect temperature, insufficient oxygen, overfeeding or
fouled water. If hydras start to die off, immediately transfer
all organisms to clean, fresh water.
When culturing green hydras (Chlorohydra viridissima)
allow for 8 to 10 hours of light per day. This organism has
within its tissues symbiotic green algae which require light
for photosynthesis.
Planaria
Upon receiving, loosen cap and aerate culture. Planarians
avoid strong light and are much more active in diffuse light.
Keep culture between 20 °C and 22 °C.
Planarians can be cultured in any type of bowl or large culture
dish. A shallow white enamel bowl filled with pond water or
spring water is suggested for easy viewing.
Planarians are hardy animals and are relatively easy to culture.
They will thrive on fresh beef liver and/or hard–boiled egg
yolks. Feeding once a week is usually adequate, depending
on the number of individuals. A pea-sized portion of liver
or yolk is sufficient for approximately 50 planarians. Allow
the planarians to feed for one hour. Then remove the excess
food or transfer the worms to a fresh bowl of water to avoid
contamination. Planaria require relatively little maintenance
and can be used in a variety of interesting experiments, making
them ideal for the classroom.
Daphnia
Upon receiving, loosen cap and aerate culture with a clean
pipet. Daphnia should be maintained in diffuse or indirect
light at temperatures from 65 to 75 °F (18 to 24 °C).
Culture Daphnia in an aquarium or vessel filled with
filtered spring/pond water or aged tap water. Suggested minimum
volume is one to two liters.
Daphnia can be maintained using one or a combination
of the following methods:
(1) Two or three times weekly exchange 50 to 100 mL of water
from the Daphnia culture with an equal volume from
a rich culture of a unicellular, non-filamentous alga such
as Chlorella.
(2) Mix one–fourth of a mashed, hard–boiled egg yolk in 500
mL of water and let it stand for one to two days to permit
bacterial growth and then exchange equal volumes of culture
water and suspension as above.
(3) Prepare a yeast suspension by adding a pinch of active
dry yeast and a pinch of sucrose to warm water, let stand
an hour or two and add one to several pipets full to the Daphnia
culture. Both egg yolk and yeast suspensions should be added
in quantities sufficient to just cloud the culture water,
the Daphnia should be able to clear the water within
several hours to a day. Periodically supplement the Daphnia
culture with several milliliters of a mineral supplement (such
as Knop's solution).
Rotifers
Upon receiving, loosen cap and aerate culture with a clean
pipet. Rotifers should be kept in moderate light at room temperature.
Culture rotifers in small culture dishes filled with pond
water. Lightly cover dishes to avoid evaporation, yet allow
air exchange.
Rotifers can be maintained using one or a combination of the
following methods:
(1) A diet of unicellular, non-filamentous algae such as Chlorella
or Chlamydomonas.
(2) Very briefly boil 20 grains of wheat in one liter of water.
Let the medium stand for a few days, then pour it into small
culture dishes and add rotifers. After several weeks, when
the rotifer culture is flourishing, divide each culture into
two dishes and add more wheat medium.
(3) Mix 0.5 grams of hard-boiled egg yolk into a small amount
of deionized water. Then add this egg yolk paste to 500 mL
of water and let stand. On the fourth, sixth and eighth days,
add rotifers to the egg media. After several weeks, subculture
the rotifers.
Vinegar Eels (Turbatrix)
Upon receiving, loosen cap and aerate
culture with a clean pipet. Vinegar
eels should be kept out of strong light
and will tolerate a wide variation of
temperatures. Room temperature should
be fine.
Culture vinegar eels in culture dishes or just about any kind
of glass or plastic container.
Vinegar eels can be maintained by placing the worms in 200
mL of unadulterated apple cider vinegar to which a two centimeter
cube of apple has been added. Cover the dish loosely to allow
air exchange but also to prevent evaporation. Subculture vinegar
eels every three to four months. Be sure to add some of the
old culture to fresh vinegar when subculturing.
Earthworms
Upon receiving, earthworms can be kept
in original container for a couple of
days if kept at approximately 15 °C
in a moist, dark place.
Culture earthworms in an appropriately sized container. The
size and quantity of worms you have will determine the size
of the container. Allow approximately 150 milliliters per
large earthworm. A dozen or so worms can be kept in a half-gallon
milk carton. Worms feed on decaying organic matter in soil.
Adding dead leaves to the soil will provide the worms with
an adequate supply of organic material. Occasionally add very
small amounts of bread or cornmeal if the humus content in
the soil is low. Excessive amounts of foods can encourage
mold growth. Always keep the soil slightly moist. Water the
soil only enough to keep it damp. Overwatering is a common
mistake. Flinn offers a complete earthworm farm including
container, bedding and food. Consult the Flinn Catalog/Reference
Manual index.
Snails
Upon receiving, put snails in an appropriate aquarium or terrarium.
Land snails should be maintained in indirect light at temperatures
from 20 °C to 22 °C. Culture land snails in a terrarium
or glass jar. First, add a one-inch layer of sand or small
pebbles; secondly, add a layer of soil and a top layer of
rotted leaves. Then add some small dry twigs and a few stones.
Mix the soil with a small amount of calcium carbonate to ensure
proper shell growth. It is also important to keep the soil
slightly moist. Land snails can be fed small pieces of lettuce,
carrots, apples, or celery. Remove excess food if it becomes
molded.
Culture pond snails in an aquarium or glass jar containing
a layer of sand or small pebbles. Add a few small aquatic
plants and fill with spring, well or aged tap water. Every
couple of days replace some water and occasionally check to
make sure the calcium level is adequate. The lighting level
should be adjusted to suit whatever plants are being kept
in the aquarium.
Always cover aquariums because snails can easily climb out.
Pond snails will feed on aquatic plants or algae. Lettuce
leaves or flaked fish food added several times weekly will
enable most snails to thrive. Uneaten foods should be removed
promptly to prevent fouling the water.
Mealworms
Upon receiving, place mealworms in a larger container with
sufficient amount of bran meal medium. Mealworms should be
kept at a temperature of 30 °C for optimal growth.
Culture mealworms in any sized flat bottom bowl or container
with the top screened or loosely covered. The size of the
container will determine the amount of mealworms. The larger
the container, the more mealworms.
Mealworms can live on a diet of any type of dry grain or cereal.
One of the best food sources for mealworms is bran meal; it
provides for a healthy, thriving mealworm colony. It should
not be necessary to add water directly to the medium or culture
container. Adequate moisture can be provided by sprinkling
freshly grated carrot or potato over the surface of the medium
once every week to ten days. Every six months, transfer the
adults, pupae and larvae to fresh media. Subculture the large
numbers into multiple containers. Mealworms are ideal for
classroom study. They´re easy to maintain and are relatively
easy for students to handle.
Drosophila
Upon receiving, store Drosophila in dim light or darkness
at temperatures between 21
and 24 °C.
Culture Drosophila in culture vials or small "milk"
bottles using commercial culture medium and equal amounts
of water. Commercial culture media are recommended for their
much greater convenience (they require no cooking), shelf
life in the dry state, and because they generally include
an effective mold inhibitor—eliminating a common problem
which often results in loss of cultures. Plug the vials with
plastic foam or nonabsorbent cotton. After a few minutes,
when the medium has set, the flies can be added to the vial.
A short length of plastic netting is often placed in the vial
to provide a surface for larvae to attach and pupate. Drosophila
can be maintained by keeping viable adults on fresh medium.
Changing the temperature will allow you to speed up or slow
down the life cycle of the fruit flies. Higher temperatures
speed up the life cycle but also promote bacterial and fungal
growth in the culture vials. Subculturing Drosophila
should be no problem once a healthy population of flies is
established. Female flies can begin laying eggs two days after
emerging from their pupal cases, and lay as many as 500 eggs
within a ten–day period. Once adult flies are introduced to
the medium they should begin laying eggs. To ensure the accuracy
and viability of test and experimental crosses, female adult
flies should be collected and isolated while still virgins.
Female flies must be removed within 12 hours of hatching from
pupal cases. Female Drosophila are able to store sperm
from a single insemination throughout their reproductive life;
parceling out the sperm each time a batch of eggs is laid.
Adult fruit flies may live for several weeks.
Aquarium Plants
Upon receiving, plants can be transplanted to an aquarium
after gently rinsing them in tap water. This removes the majority
of bacteria and other contaminants. Maintain these plants
in medium light at temperatures from 18 °C to 24 °C.
Culture plants in an aquarium. Add one to two inches of clean
sand or small gravel to the aquarium. Fill with well, rain
or pond water. If tap water is used, it must be allowed to
age for three days. Add plants to the sand and space them
about eight to ten centimeters apart. Cover the aquarium lightly
to restrict evaporation and allow ventilation. Keep plants
in a medium light. Strong light will encourage algal growth
which is detrimental to plant growth. If you´re keeping other
animals in your aquarium, such as fish or snails, make sure
not to overfeed them. Overfeeding pollutes the water with
organic wastes. Check your aquarium daily for dead plants
or animals. Always remove all waste from the aquarium as it
accumulates.
Carnivorous Plants
Upon receipt, plants are ready to be transplanted. Carnivorous
plants should be maintained in moderate light at temperatures
from 18 °C to 24 °C. Direct sunlight can elevate
the temperature in a terrarium to levels high enough to burn
or kill the plants within.
Culture carnivorous plants in a bog terrarium. Place one inch
of gravel at the bottom of the terrarium. Coarse charcoal,
up to equal parts charcoal and gravel, is often recommended
in bog terrariums. Then mix acid bog soil with some sphagnum
moss and cover the gravel. One part garden or potting soil
mixed with two parts commercial peat will make an adequate
acid bog soil. Add enough pond or aged tap water to cover
the gravel but not the soil. Loosely wrap the roots of the
plants in sphagnum. Set the pitcher plants in soil deep enough
so the roots can grow into the water. Venus fly traps should
be set so their root tips grow in the soil just above the
water level. The sundew plants should be planted toward the
top of the soil since they do not require as much water. Handle
the plants gently and don't allow them to dry out. Water the
plants once a month or when no more condensation appears on
the glass. Keep the terrarium covered with a piece of glass
or plastic film. These plants require high humidity. Aerate
once a week. These plants are adapted to nitrogen–poor soils
and have evolved elaborate insect trapping mechanisms as a
source of supplementary nitrogen. Occasionally you may wish
to feed these plants.
The sundew can be fed vestigial winged fruit flies. For Venus
fly traps, drop cut up Tenebrio larvae (mealworms)
or small bits of meat into the plant's trap. Pitcher plants
can survive long periods without any "dietary" supplements,
relying on photosynthesis and nutrients derived from the planting
medium.
Classroom Plants
The plants can remain in the pot supplied
and transplanted to a larger container
as necessary. A good general–purpose
potting soil can be used, or else a
mixture of equal parts peat, sand, and
loam. Humidity should, for most plants,
be kept at approximately 50%. Temperatures
should range from moderate to warm (18
°C to 25 °C). Lighting should
be medium to bright;protecting
bright light plants from excessive heat—with
an average duration of about 15 hours
per day. Feed plants (follow product
directions) once every month with a
liquid fertilizer. Specific requirements
for plants are listed in the Flinn Scientific Catalog/Reference Manual.
Mimosa pudica is known as the sensitive plant.
It curls its leaves in response even when only lightly touched
or shaken. Mimosa will do best in a soil mixture of
two parts peat moss, two parts loam, and one part sand. Keep
soil slightly moist. This plant requires high humidity and
warm temperatures. Keep plant in a covered terrarium or greenhouse
and expose to bright light several hours a day.
Coleus is one of the most easily grown potted
plants. Keep at warm temperatures and in bright light. It
is very susceptible to mealybug infestation. If heavily infested,
it is probably best to discard the plant, since they can be
obtained very easily. Periodically pinch back stem tips and
buds to encourage branching and a fuller plant.
Geraniums are also easily cultured and can be grown in medium
to bright light at moderate temperatures. Transplant individual
plants to 4–inch diameter or larger pots. Again, pinching
back stem tips will encourage fuller growth and also promote
flowering.
Seeds
Upon receiving, you may plant or store the seeds depending
on your needs. Store the seeds in an airtight bag at temperatures
between 5 °C and 15 °C in a dark, dry place.
When you are ready to plant the seeds, there are a few things
you can do to ensure seed growth. Make sure the seeds are
loosely covered with a sterile starter mix. An all-purpose
potting mix (such as Jiffy Mix®) or milled
sphagnum moss make excellent germination media. The starter
medium should be placed in seed trays or small pots to a depth
of two to three inches. Drainage can be facilitated with a
thin layer of gravel beneath the soil. Some seeds can be soaked
for 12 to 24 hours prior to planting to speed germination.
As a general rule, seeds should be sown at a depth of up to
three times their diameter. Small seeds can be scattered over
the soil and lightly pressed down. Water the seeds by gently
sprinkling with warm water. Cold water could lower the temperature
of the soil below the germination level. Always keep the soil
moist. Cover the seeds with a pane of glass or plastic wrap
to trap heat and conserve moisture. Try to keep the seeds
at 22 °C to 27 °C. After the seeds have germinated,
remove the glass and use fluorescent lights to warm the seedlings.
As soon as the seedlings can be handled, transplant them to
larger containers, leaving enough room for each plant to grow
unrestricted. As a general rule, seedlings are ready to be
transplanted at the time the first foliage leaves appear.
Water regularly.
Choosing the right water from the right source is the single
most important factor when using many of the methods described
here. Spring, stream, or pond water—filtered or sterilized
before use—are the best sources for culture water, with
a few exceptions.
Defined media; those which contain measured quantities of
several minerals, salts or supplements; are generally made
with distilled or deionized water. These are the only media
for which distilled or deionized water are appropriate. Distilled
and deionized water lack essential trace elements and cultures
placed directly in either type of water will be subject to
severe osmotic stress.
Occasionally aged tap water is called for. During the aging
process—when tap water is left for several days in an
open container—chemicals, such as chlorine, gas–off from
the water rendering it somewhat more hospitable. Other treatment
chemicals and pollutants may remain at sufficient levels to
harm or even kill extremely sensitive organisms. Avoid tap
water unless specifically recommended, or as a last resort.
When obtaining water from natural sources (ponds, streams
etc.) take pains to find a source as free of pollution as
possible. Likely sources of pollutants are nearby industries
or areas of intensive agriculture. |
| |
| |
| © 2006 Flinn Scientific,
Inc. All rights reserved. Reproduction
permission is granted to science
teachers who are current customers
of Flinn Scientific, Inc. No part
of this material may be reproduced
or transmitted in any form or
by any means, electronic or mechanical,
including, but not limited to
photocopy, recording, or any information
storage and retrieval system,
without permission in writing
from Flinn Scientific, Inc. |
| |
|
| |
|
