The Unseen World

Like many aquarists, I have spent hours on end watching my aquarium. The diversity of animals living in the glass box in my living room is a constant source of amazement for me. For the first two years I had a reef tank, it seemed I could find a new critter each and every time I spent more than five minutes looking. I've also spent hours with a magnifying glass examining the smaller animals that live on the rocks and in the substrate near the glass. These magnified examinations showed me a whole new range of animals that had previously escaped my notice. Even with all the animals I had found with my own eyes and a magnifying glass, I was still shocked at the number and variety of fascinating animals living in my system that could only be seen and appreciated through a microscope.

Microscopes range in price from $20 children's toys to $75,000+ research lab equipment. I bought my first microscope the same way I purchased my first digital camera. I did some research over the web and learned about the basic types of equipment and price ranges. I eliminated both the toy scopes (knowing they would be useless) and the high-end scopes (knowing they would be overkill). I wanted my first microscope to be a moderately priced piece of equipment that was good enough to give me an idea of whether or not I would enjoy microscopy without breaking the bank. (Pretty much the same way I took up reef keeping: I started with a thirty-gallon acrylic tank and upgraded to my current setup after I was sure that I liked being an aquarist.) In the case of the microscope, my first purchase was a National model 138 (which was listed as a high school level scope) that I bought online for about $250.

Microscopes, like any good camera, are all about the quality of the optics. Obviously, the quality of the image from a $250 microscope is not in the same league with a microscope costing $2,500 or more. While my $250 microscope would not be appropriate for someone who had to spend hours on end staring into it, for casual use in a hobby situation it has been ideal. I've been using my National scope for three years now and I've had lots of fun and learned more than I could have imagined. The following are some of the photographs I have taken through the eyepiece of my microscope using a digital camera.

Foraminiferan test-
This calcium carbonate shell enclosed a single celled amoeba which extended slender pseudopods from the pores in the shell. These shells look like delicate works of art through the microscope.

Harpacticoid copepod-
The single red eye helps identify this animal as a copepod. The first time I saw one of these, I was reminded of a trilobite.

Hydrozoan jellyfish-
This little guy is smaller than the period at the end of this sentence. It was fun to watch him pulsing around in the Petri dish. He is photographed against strands of Bryopsis.

The transparent shell allows you to clearly see the internal organs of this bivalve.

Polychaete worm-
This closeup of a transparent polychaete worm shows the jaw structure that resembles pliers. I could watch this worm exert the jaws, grab a food particle and pull it back inside.

The name means "wheel-bearer" and after seeing a live one under the microscope you know why. These animals have what look like spinning wheels on their head that create a water current that draws food particles into the mouth.

A. percula larvae-
You can clearly see the yolk sacs and eyes on these eight day old clownfish larvae. They are still encased in their transparent egg shells.

I found quite a large population of these tiny hydroids living on the walls of my sump along with sponges.

This is a true relative of terrestrial spiders that I found in the debris at the bottom of my sump. After seeing the number of animals living in my sump debris, I no longer "clean" my sump!

I frequently find empty shells from this type of snail when I examine substrate from my tanks.

Pocillopora polyp-
This 30X magnification of a Pocillopora polyp shows the round white acrospheres at the end of each tentacle.

Pocillopora acrosphere-
One acrosphere flattened beneath a cover slip shows hundreds of nematocysts. The golden brown objects are zooxanthallae.

If you have been considering the purchase of a microscope to get yourself started in this fascinating world of discovery, here are just a few of the basics.

High-Power vs. Low-Power:

The two basic types of microscopes are high-power and low-power.

High-power microscopes generally have three to four distinct magnifications: 40X, 100X, 400X and sometimes 1000X. High-power scopes are used to look at very small things such as single cells or bacteria that are mounted on a microscope slide. Microscope slides are pieces of clear glass approx. 75mm long, 25mm wide and 1mm thick (3"x1") and are generally used with cover slips. Cover slips are pieces of glass approx. 22mm square and .17mm thick. (Cover slips are VERY thin and VERY easy to break!) For a simple "wet mount", a drop of water is placed on the slide and a cover slip is placed over the top of the drop. The slide is then placed on the stage for viewing. Since the lighting on the high power scope comes from below the specimen, the specimen needs to be transparent. (Fortunately, most of the very small animals are, for the most part, transparent.)

Low-power microscopes (also called dissection or stereo microscopes) are used to look at larger objects, such as grains of sand or small animals such as brine shrimp or small starfish. (By the way, they're also handy for checking the settings on your jewelry or removing splinters from your fingers!) The specimen is placed in a Petri dish (shallow glass dish about four inches across) that allows the aquarist to observe the animal moving around in the water. My low-power scope has lights above the specimen and below that can be independently operated, so the specimen can be illuminated, even if it is opaque. The dual objective lenses produce a three-dimensional image. These scopes come in a variety of powers from 10x to 80x, with the most common being combinations of 10x/35x and 20x/40x.

I own one microscope of each type. If I my budget had only allowed for one microscope, I would have chosen the low-power microscope. I frequently fill a Petri dish with macro algae and substrate from the tank, refugium or sump and hunt for new critters while watching the isopods, worms, copepods, nematodes and myriad other animals go about their business. I also have examined small starfish, brittle stars, snails, coral fragments and whatever else I could catch, under the low-power scope. It is amazing to be able to see the detail of these small animals. I also use the low-power microscope to find specimens that I want to examine further under the high-power microscope.

The high-power microscope has been great for examining small living animals like ciliates and protozoan as well as coral cells and structures such as nematocysts. A drop of water and small bit of algae in a depression slide can contain dozens of single-celled animals swimming around. (Unlike regular microscope slides that are flat glass, a depression slide has a circular depression in the center that will hold several drops of water. Cover slips are generally not used with depression slides.) I have snipped off tentacle tips from various corals (Plerogyra, Catalaphyllia, Pavona) and compared the size and structure of the nematocysts. A ground up tentacle from an Aiptasia is ideal for studying zooxanthallae. (Finally, a good use for Aiptasia!)

Binocular vs. Monocular:

Binocular microscopes have two eyepieces for viewing. Monoculars have one eyepiece. Binocular scopes are much easier on your eyes for extended viewing sessions, but they are more expensive.


Supplies - Items such as microscope slides, cover slips, Petri dishes and basic dissecting kits (which contain necessary tools like tweezers, small scissors and probes) can all be found and ordered online.

Mechanical stage - The stage is the flat surface where microscope slides are placed for viewing. The least expensive microscopes will simply have two clips to hold the slide in place. I highly recommend upgrading to a mechanical stage for a high-power microscope. A mechanical stage has a spring-loaded arm to hold the slide, and two knobs to position the slide. One knob moves the slide right and left and the other moves the slide up and down. Many of the small critters I have examined move around quickly in their drop of water and the mechanical stage allows me to move the slide smoothly to keep up with them.

Carrying case - A plastic carrying case with foam insert for storing the microscope when not in use will help to insure that your microscope does not get damaged.

Reticle - Is a special eyepiece that has an inscribed scale (right) that allows you to measure the specimens you are viewing.


The pictures that I took in this article were shot using an Olympus E-100 digital camera mounted to a tripod with the front lens of the camera directly against the eyepiece of the microscope. This system works for me because the viewfinder of my digital camera has through the lens metering and a pretty good zoom lens. I look through the camera, into the microscope and use the focus on the microscope to adjust the fine focus on the image I am photographing. The major drawback of photographing in this manner is that I am not able to capture the entire microscope image in the camera. I get a narrower field of vision through the camera. This means that sometimes I have to switch down to a lower magnification lens in order to capture the whole specimen I am trying to photograph. While this system is certainly not ideal (or even elegant), it works and I have been able to take pictures to share on my website.

In Conclusion:

I would certainly recommend either of these National microscopes to anyone getting started. They are reasonably priced, easy to use and will provide a window into a fascinating new world. (They are available at

Be forewarned, those of you who decide to get yourselves a starter microscope. If you're anything like me, you could become obsessed with the unseen world and find yourself looking to upgrade your microscope one day. As it happens, my upgrade arrived last week. It is a used Olympus BH-2 that I bought from a veterinary pathologist. (And, yes, it ended up being about nine times more expensive than my National scope.) Buying a more sophisticated piece of equipment opens up a whole new "can of worms", as they say. You would be surprised at the variety of types of microscope configurations available! You have to learn a whole new set of terminology regarding lighting and optics; then, of course, is the five hundred page book you have to read in order to learn to use the thing. But, so far I'd have to say the added expense and complexity has been well worth it considering the quality of the images. (And heck, I don't even really know how to use it yet.) However, if I had not been using the starter scope for the last three years, I'm not sure I would truly appreciate the resolution and clarity of the images my new microscope provides.

Now this is a microscope! It weights over twenty pounds and has more knobs than I can shake a stick at. I still have to purchase an adapter for my Canon F-1 camera, so I'm shooting pictures with the digital camera through the eyepiece. I can't wait to be able to take proper pictures of the whole field using the trinocular head!

Here's a sample of a munnid isopod photographed through my Olympus microscope.
Awesome, huh?

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The Unseen World - by Sandra Shoup -