Materials: A large glass jar, fresh and unfertilized garden soil, water, hot plate, celophane foil

Method:

• Fill the glass jar with a few centimeters of the garden soil.
• Add non-chlorinated tap water to the soil and fill the jar with the water (3/4 full).
• Boil the soil-water mixture for about 30 min. This will kill off bacteria in the soil and will extract nutrients from the soil. Bacterial spores may survive the boiling, as they are heat-resistant. This is not a problem, though. These bacteria will serve as a food for other microorganisms later on.
• Cool the water to room temperature and let the soil settle to the bottom of the glass jar. Do not filter the soil away. The soil will continue to supply nutrients and will act as a buffer.
• Add a small amount of pond water which contains algae. Do not add too many algae. You may want to scrape off some algae from rocks or take a few algal filaments floating in a pond.
• Cover the jar with celophane foil. This will allow for gas exchange and prevent dirt and dust falling into the water. It also reduces evaporation.
• Wait a few weeks for the algae and ciliates to develop. With a bit of luck, paramecia will grow and form white clouds in the water. The color of the water may also change, an indicator for algal growth.
• Store the jar in a bright place but not in direct sunlight.
• Using a pipette, extract some of the microorganisms to be observed under the microscope.

Troubleshooting:

• Microorganisms do not form: This is probably due to the fact that there were none or not enough in the pond water which was added.
• The water starts to smell bad: This may be due to the system becoming anaerobic. Make sure that enough oxygen is able to enter the water. Paramecia and other ciliates are probably dead by now…..

Materials: A hand full of hay, a large beaker, pond water, some milk

Method:

1. Take a hand full of dried grass or hay (free from pesticides or herbicides) and cut the grass into smaller pieces
2. Place the cut grass into the beaker and about 0.5-1 liter of water.
3. Add 1-2 drops of milk. The water will turn slightly turbid. The milk is food for the bacteria and they will start to reproduce. The ciliates feed on the bacteria and will also reproduce.
4. Let the beaker stand open for several days, protected from direct sunlight as this may result in overheating and the heat will reduce the oxygen concentration. Do make sure that the beaker receives sufficient light, though. Photosynthetic algae present in the pond water will produce oxygen.
5. Keep adding 1-2 drops of milk when the turbidity disappears. Bubble some air through the water at regular intervals (using an air-pump from an aquarium) or agitate the water a bit to enrich it with oxygen.
6. Replace the evaporated water.
7. Take some sample from the surface of the water (where there is oxygen) for microscopic investigation. If the water is agitated, then the microorganisms are (of course) not able to collect beneath the water surface.

Troubleshooting:

Problem: The water starts to smell.
Solution: This is normal. Bacteria are starting to decompose the hay and the added food. If bubbles start to appear though, then this is an indication that methane is formed anaerobically. This should not be and indicates that there is not enough oxygen in the water.

Problem: There are many bacteria but too few protozoa in the water.
Solution: Probably there was overfeeding. Add less milk and less hay. The bacteria multiplied too quickly and the protozoa could not keep up.

Problem: Nothing much seems to happen after a few days
Solution: Did you use chlorinated tap-water? Was the hay treated chemically?

Materials: Fresh pond water, wheat grains, glass beakers

Method 1:

1. Pour some pond water containing ciliates into the beakers and place 1-2 wheat grains into the water.
2. Wait for 2-3 days. The wheat grains will start to decompose and will seem to form a slimy layer around it. There should be thousands of ciliates in this slime. We have established a small food chain. Bacteria will break down the wheat grain. Paramecia will feed on the bacteria and reproduce.

Troubleshooting:

Problem: No paramecia have formed.
Solution: There were probably none in the original water sample. Paramecia and other ciliates can be found on the ground of ponds, in the slimy surface of rocks, etc. Include some of this material as well.
Solution: Did you use a complete wheat grain (with seed coat)? If you use rice or other polished cereals, then there are not enough nutrients available. The seed coat contains DNA and proteins (phosphates and nitrogen compounds) which are used by the bacteria.