tank experiment. How do you want the average plant height recorded?
growth. Should we add any fertilizer (want kind and how?) to equalize the two tanks?
A: You will need to put all 4 trays as close to the sides as possible, leaving a space down the center of the tank. It would be best if you place the powerhead directly on the bottom of the tank, aiming the stream of water down the center of the tank. Do not use the foot or suction cups on the powerhead at all. The heater will then have to go along the short end near the powerhead. It will be tight, but it is possible. The sponge filter can be bent if need be.
A: We need to know which trays have 75% sand/25% soil and which have 25% sand/75% soil in order to use your data. It would be best if you labeled each tray as 1,2,3, or 4 in tank B. Then when you send the plant height data, average only the 2 that are alike. Otherwise, the experiment's results will not be clear.
For example, if trays B1 and B2 were 75% sand/25% soil and had heights of 1 inch and 1.2 inches respectively, the average would be 1.1 inches for 75% sand/25% soil. Then if trays B3 and B4 were 25% sand/75% soil and had heights of 0.6 and 0.8 inches respectively, the average would be 0.7 inches for 25% sand/75% soil. You can just write the averages below instead of in the box all the way to the right. Make sure to indicate the type of sediment mixture each tray contains
A: Please contact Mark Lewandowski at 410-260-8634 or email him at firstname.lastname@example.org. He will send you any equipment that you are missing.
A: At least one day before you want to plant the seeds, break each pod into several pieces. Squeeze out the seeds and gelatinous substance that encases them into a jar of cold water. Place this jar in the refrigerator until you need them. The gelatin will break down in about 24 hours. You can then pour the contents of the jar through a coffee filter placed in a large beaker or plastic container, or you can pour the water out of the jar (the seeds sink) and then dump the seeds onto a paper towel. Divide the entire amount of seeds into 8 parts (easiest way is to divide the pile in half, then each of those piles in half, etc) and proceed as in the protocol.
Q: Why do I need to fill out the "Experiment Diagram and Growth Chamber Set-up" form?
A: This form tells us how your tank has been set-up for your experiment. For example: If you are performing a light time experiment, this form will tell us that Tank A receives 24 hours of light and Tank B receives 12 hours of light. Without this sheet, we cannot use your data. Make sure to fax this sheet to (410) 260-8859.
A: The time it takes for germination depends on the temperature of the water. Make sure to turn your lights on as soon as possible. If your seeds have not germinated after 2 weeks of the lights being on, let us know.
A: Turn your powerhead off for several days to a week. The particulates in the water will drop out and the water should become clear.
A: Just before you are ready to use them to plant, decant the water carefully off of the seeds and use a spoon to divide them into 8 equal portions. You can also pour the water and seeds onto filter paper to strain the seeds and then divide them into 8 equal portions.
A: This depends on which project you are doing. For wild celery, set aside 24 cups of sand before you mix the sediment. Mix each of the 8 seed portions with 1 cup of sand and sprinkle on the sediment surface. Use and additional 2 cups of sand to cover the seed layer. For sago pondweed, set aside 12 cups of sand before you mix the sediment. Use two cups of sand per tray to cover the sediment mixture.
A: No, they don't. The "Dark Cycle" is somewhat of a misnomer. The metabolic activities described by the D.C. are carried on all the time; it's just that in nature they are a greater proportion of the total activity when there is no light.
A: That is a much better technique, really. We considered asking teachers to do that, but it takes more time and raises a lot of questions about how to make the randomization technique consistent between schools. Unfortunately, unless you are consistent with the activities of others, your data may not be comparable. Why don't you measure greatest height in addition to what you are doing and compare the results. We could put your report on the web site for other teachers to learn from. This might make a good student activity.
Q: The nitrates in one of our tanks are close to zero and I know that a certain level of nitrates is needed for plant growth. Should we add any fertilizer (want kind and how?) to equalize the two tanks?
A: Having a nitrate level close to zero doesn't mean your water is low in nutrients. Nitrogen exists in many forms in water, and the primary source used by plants is ammonium. Even if the water had no nitrogen whatsoever, the plants could still grow fine using the nitrogen they extract from your nutrient rich potting mixture. Adding nutrients will stimulate algae growth, and would probably have little or no effect on plant growth.
Why do you suspect your tanks are different? Challenge your students to come up with some potential reasons. At first it seems counterintuitive that the tank with more sand and less topsoil has higher nitrate levels, but from the comment that there are twice as many plants in the high sand tank and from seeing that the pH and Hardness are higher in the high sand tank, I suspect that the plants are having a greater effect on the water quality in this tank and may be consuming the nitrates, thus removing them from the water (see our new Web page "pH, Hardness and Nitrogen Information"). Since your initial water quality data showed 5 mg/l Nitrate, any level lower than that must have been occurring as a result of consumption.
On visiting Forbush School and Aberdeen Middle, I saw that several of the tanks were very off-color. We immediately set up our own, identical system to see where the problem came from. It seems as if the topsoil brand we used has a lot of fine particulates in it. If your layer of sand is thin enough to expose topsoil when the trays are submerged, some of the topsoil will mix with the water and discolor it, possibly to the point where you can barely see your trays. If this happens, turn off your powerhead for two days to let the particulates settle out.
To prevent this problem, be sure to completely cover your topsoil with sand before submerging your trays. It’s important not to bury the seeds too deeply, but up to 1/4 inch of sand can be used without harming the seeds.
A: I found the same problem– as each new thing was turned on, the surge protector would trip. Once everything was hooked up, though, it was fine. Try plugging everything into the strip with the strip switched off, and then turn the strip on.
A: The gray film from the sand is nothing to worry about. It will settle out over time and won’t affect the plants at all. The filters should be cleaned according to the instructions on the package they came; a simple rinse under luke warm water once per week.
For more information, contact
Mark Lewandowski 410-260-8634.
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