Your microscope
What you see under the microscope · Pond water
Pond water under the microscope: paramecia, tardigrades and algae
A drop of water from a pond or from damp moss, under a coverslip. To the naked eye there is nothing; under the microscope, a world that swims, spins and feeds.
Try darkfield in the panel: it is the classic technique for pond life.
40×: moving dots
With the lowest-power objective you see specks crossing the field. The largest, rolling like green balls, are volvox colonies.
100×: who's who
Now you can recognise them: paramecia swimming as they spin on themselves, spirogyra filaments with their green spiral ribbon, diatoms like little golden boats and, if you are lucky, a tardigrade walking slowly.
400×: following a paramecium
You have to move the stage so as not to lose it. You can see the cilia that propel it, the oral groove through which it feeds and the contractile vacuoles, which fill and empty to expel excess water.
Speeds are shown slowed down so you can follow them. Try fluorescence in the panel: only the algae glow.
The tardigrade, up close
An eight-legged animal with claws, about 0.25 mm long, famous for surviving desiccation. It lives in damp mosses and lichens and in ponds.
3D view: the microscope sees a single plane.
Which microscope do you need to see this?
For pond life, 40×, 100× and 400× are enough. Darkfield makes it far more spectacular: it comes as standard on some models at 1000×, and at lower magnifications you can get it with a darkfield stop in the condenser.
Which microscope do I need?Frequently asked questions
What can you see in a drop of pond water under the microscope?
Protozoa such as paramecia, algae such as spirogyra, diatoms or volvox, small animals such as rotifers or tardigrades, and bacteria.
What magnification do you need to see paramecia?
You can see them moving at 40×, recognise them at 100×, and at 400× you can make out the cilia and the vacuoles.
Where can you find tardigrades?
In the water that comes out of damp moss when you squeeze it, and at the bottom of ponds.
What is darkfield?
A way of illuminating in which only the light scattered by the sample reaches the eye: the organisms shine against a black background.
What can you see in pond water with fluorescence?
Without staining anything, the chlorophyll in the algae glows red under blue excitation light: you see the algae and not the protozoa. You need a microscope with fluorescence equipment.
How this simulation is made
It is not a photograph: it is a calculated model. Magnification, field of view and resolution come from each microscope's spec sheet; the sample measurements come from the sources cited below.
| What | How it is calculated | What is approximate |
|---|---|---|
| Magnification and field of view | Magnification = eyepiece × objective. Field of view = eyepiece field number ÷ objective magnification. | Exact according to the spec sheet. |
| Sizes | Paramecium 250 µm (170–330), euglena 50 µm, diatom 40 × 7 µm, volvox 300 µm, tardigrade 250 µm (112–293). | Simplified shapes; tardigrade width without a source. |
| Speeds | Euglena 95 µm/s, diatom 10 µm/s, tardigrade 163 µm/s; volvox rotates at 1 rad/s. | Shown at one fifth of the speed so you can follow them. For the paramecium the sources disagree (from 0.06 to 1 mm/s): we use 1 mm/s. |
| How many there are | We put many different organisms together in one drop. | A real drop may contain far fewer, or far more of a single species. |
| Darkfield and phase contrast | Brightness according to the slope of the surface and the optical phase shift. | Qualitative approximation. The instruments in the shop with darkfield as standard do it at 1000×; at 100× and 400× you need a darkfield stop in the condenser, which Euromex offers as an option. |
| Fluorescence | Chlorophyll autofluorescence: under blue (or UV or green) light it emits in the red, around 680–685 nm. The algae glow (spirogyra, volvox, euglena, diatoms); anything without chlorophyll stays almost black. | Intensities chosen by eye. The faint green glow of the euglena's eyespot has been described, but not its intensity. |
Sources
- Spec sheets of the Letscopes microscopes.
- Paramecium caudatum (Wikipedia); speed: BioNumbers and PMC6187482.
- Euglena: PNAS 2017. Diatoms: Diatoms of North America and PMC11962607.
- Volvox: Drescher et al., PRL 2009 and BMC Biology 2010.
- Tardigrades: PMC11410187 (size) and Nirody et al., bioRxiv 2021 (gait).
- Darkfield: Nikon MicroscopyU.
- Darkfield as standard (cardioid condenser and S100× oil objective with iris, 1000×): Euromex, iScope darkfield and bScope darkfield.
- Chlorophyll fluorescence: Donaldson L., “Autofluorescence in Plants”, Molecules 2020 (MDPI), and Takahashi T., Molecules 2019 (PMC6943654).
- Green fluorescence in microalgae and in the eyespot of euglenas: Tang and Dobbs, Applied and Environmental Microbiology 2007 (PMC1855647).
Other samples
Not sure which microscope to choose?
Tell us what you want to see and who it is for, and we will recommend the right instrument.
Letscopes advisorMicroscopes for schools