Microscope advice

Samples, slides, and pictures

From a slimy patch in your tank to a clear picture you can share.

1. Collect a sample

• Take the stuff you are worried about. A small piece of the film, mat, or strings is plenty. A clean pipette or a turkey baster works well for sucking up film from sand or rock. Try to avoid scooping up whole grains of sand, which are in the way later.
• Use a small, clean container such as a vial or cup, with some tank water, not freshwater. Collect from more than one spot if the growth looks different in different places.
• Look at it soon. Living cells are much easier to identify than dead ones. Keep the container at about tank temperature, out of the sun and away from heat.
• Note where in the tank you took it from, and when.

2. Make a slide

A simple "wet mount" is all you need. You will want glass slides and larger rectangular cover slips (see what to buy). Practice first with plain RO water, with no sample. You can just wipe the slide and cover slip clean and try again until it comes easily.

1. Start with a clean glass slide and a cover slip.
2. Put one small drop of tank water on the slide, and add a tiny bit of your sample to it. Beginners almost always use too much water.
3. Rest the cover slip on the slide with one edge beside the drop, not touching it, and the other side held up.
4. Slowly slide that edge toward the drop until it touches. When it does, the drop changes shape: instead of a dome it spreads out along the cover slip, pulled by adhesion.
5. Slowly lower the raised side until the cover slip is all the way down, floating on the water beneath it. With luck, not much water spills out the sides.

• Thin is better. If the cells are tightly packed or piled on top of each other, make a new slide with less sample and a little more tank water. A big clump of material will not let you see single cells.
• Give it a minute. If you let the cells settle on the slide before you look, nearly all of the Amphidinium, for example, will be seen sliding smoothly along the glass.
• Do not let it dry out, and do not leave it under the light too long. The heat from the lamp can make a cell you are watching burst. Lower the lamp's brightness, and make a fresh slide if you need a longer look.
• If you are new to focusing, see focusing: the crayon line or the edge of the cover slip gives you something to focus on.

3. Find your cells

Put the slide on the stage and start with the lowest-power objective to find where the cells are. Center a group of them, then step up to 10X and then 40X, refocusing each time with the fine focus. Then focus up and down through a cell to see its shape. If the picture looks dull or uneven, check your illumination. Look at several parts of the slide: one cell can be misleading.

4. Take pictures and video

You can take a picture through a microscope with a small point-and-shoot camera or a smartphone. Recent phones work much better than those from before 2008.

1. Set the microscope up so you have room in front of it to rest your elbows, and brace your arms on the table or a stack of books.
2. Hold the camera up to the eyepiece, but not touching it. Hold it a short distance back, about where your eye would be (1 to 2 cm).
3. Watch the display for a bright circle. Move the camera until the circle is centered and mostly fills the screen. A black border around the edge is normal.
4. A 3D-printed or cheap plastic phone holder makes this much easier, and lets you take video or stream to a monitor.

• Take video first. Motion is often more useful than a still image for identifying algae. A ten-second clip of one cell and one of a whole field of cells are both useful.
• Take stills at several magnifications, for example 40X to 100X for the overall picture and 400X for individual cells, and note which objective you used.
• Keep the files at full resolution.

5. Work out what you have

Now compare your pictures and video with the guides:

• Start with Is it a dino? to tell dinoflagellates, diatoms, and cyanobacteria apart.
• If it looks like a dino, go through the ID guide and compare the shape, the size, and above all how the cells move.