The Desk Aquarium: How to House Your Leech in Style

AQUARIUM 03SETUP 02Sanguinis:  Leeches, like cats and some humans, are cultured and DISCERNING creatures who require elegant and well-appointed accommodations.  We do NOT do well in a muddy jar, forgotten behind your pile of last year’s Popular Mechanics!  We need light, cool temperatures, and a well-ventilated home with at least a MODERATE degree of class, balance, and sophistication.  Fortunately, providing a classic and comfortable home suitable for your watery family members can be done with minimal construction mess and expense.  REALLY, with just a bit of ingenuity, you can create a home that even a sophisticated being such as MYSELF would be proud to inhabit!

cat relaxed
One of the other cultured creatures

Since I wasn’t around at the time, The Proprietor will have to tell you how to do it:

Recipe for a Home For a Discerning Leech:

One thrift shop aquarium without hood, 4-10 gallon
Aquarium base about 1/2″-1cm larger than aquarium footprint, cut  from 3/4″ high density fiberboard or plywood
Flexible or wall lamp with fluorescent or LED 100w bulb
Flat rocks as needed
Half to full bucket of lake bottom or marsh mud
Plastic milk bottles with lake or creek water
Scavenged pond plants

Clean aquarium thoroughly with soap and water, followed by a small amount of bleach water to sterilize.  Rinse thoroughly and dry.  Cut a base from smooth, high density fiberboard (HDF) or plywood, slightly larger than footprint of tank.  Seal surface with wax finish (e.g., Briwax), varnish, or paint.

Fill aquarium with about 2″ of mud, the gooier the better.  This should contain a population of worms and other bottom-dwelling creatures that will emerge and create a community as the aquarium settles.  Use flat rocks to wall off one back corner to within 3-4″ of intended water surface level, packing mud or lake soil behind rock for support and planting area.  Deep-rooted plants may be incorporated in to this soil as the wall is built up.  You will probably add to the plants as you explore neighboring ponds and marshes.  Add other rocks as your artistic sense dictates.df940830Gently fill aquarium to within 3″ of top with pond water.  Add collected rooted and floating plants, waterlogged sticks, etc.  The higher elevated area behind the rocks should be planted with shallow-water marginal plants, while deeper species go in the main part of the tank.  Leave top uncovered for ventilation and to allow rushes, sedge, grasses, Equisetum, and tall species to grow up.  Include some duckweed and other surface plants – duckweed roots are mini-ecosystems by themselves, and are one of the best places to find organisms such as hydras, Vorticella, and Stentor.

Mold can be a problem in this moist environment, and certain types of plants are particularly susceptible.  In the moist Northwest environment, partially covering the top of the tank  with a glass sheet to slow evaporation, or using a hood and lamp, led to mold overgrowth on plants and exposed glass.  This problem was minimized by leaving open the top of the tank open, letting reeds and grasses grow tall, using long-armed office lamp for lighting, and replacing evaporation with lake water.

The aquarium will be a muddy mess for 24 hours, but will gradually clear and settle.  Watch carefully over the next two weeks as the population of water creatures crawls out and establishes itself.  Algae will grow, snails will wander the glass and plant stems, and careful watching will be rewarded by glimpses of of hydras, oligochaete worms clad in fragments of duckweed leaves and wood, shrimp, and planarian worms.  Leaving the light on 10 hours/day will pump energy into the system, and such tanks can be active and self-sustaining for months without cleaning or aeration.  Having plenty of plants seems to be key to sustainability and balance – bodies of water with no plants steadily develop overgrowth of algae, while those with copious plant material stay clean, healthy and clear.

Note – I use my small aquarium as a final repository for all interesting specimens, with at least a small aliquot being added.  This builds up the diversity of the tank.


The ideal vessel for pond water studies is the thrift shop “mini-aquarium.”  Start prowling the glassware aisle your local GoodWill stores.  Among the tall, ugly old vases, look for the occasional roughly cubical or cylindrical glass container 6-10″ across and roughly as deep.  The low profile permits planting, trimming, and sample extraction, and provided a good surface to volume ratio for gas exchange.  Try to get one with reasonably smooth glass for optimum photography.  These are actually superior to traditional aquaria – the all-glass construction is sturdy, they can be picked up and moved without breaking when full, they can be readily washed out in the sink between uses, and the size is just right for a couple of yogurt containers worth of mud, water and plants.MINI AQUARIUM 20170706_123851

The same principles apply – lots of plants, ideally some mud at the bottom, and a little $5 thrift shop desk lamp for light 10-14 hours a day.  Don’t feed (see below) for a couple of weeks until everything get established, then top up with hay infusion.  These are ideal single-source specimens;  if you have three or four containers, label each one with the source, and observe the differences in flora and fauna at each site, as well as the population differences as the seasons progress.

Thrift shop mini-aquaria in my hotel room

Cleaning the inevitable accumulation of algae from the less even glass is a bit harder, but can be done with a slender razor blade scraper made from a steel-backed razor blade and a thin piece of steel rod.  When the specimen is returned to its source and the little tank is cleaned, stubbornly-adhering algae can be removed with toothpaste or a fine scouring power like Bon Ami (Canada) or Barkeeper’s Friend (USA).

Stay away from plastic containers – hydras and other creatures cannot attach to this surface to be observed, and scrubbing off persistent algae inevitably scratches the plastic.

Outdoor Ponds:

The same principles can be used to build small and attractive outdoor ponds in large pots or planters, and these can be an alternative to an indoor aquarium.  The planter is cleaned, andFRONT POND rocks or a bamboo meshwork is built to wall off about half of the planter’s volume.  This area is filled up to just below the intended water level with marsh mud and plants, then the planter is topped up with lake or creek water.  A small decorative pump and water feature can be added, but with sufficient numbers of plants in the system, water stays clear and fresh without circulation or filtration.  A small amount of pond plant fertilizer can be added if needed, and evaporation is replaced by fresh lake water (I can be found at odd  hours filling bottles at local ponds and boat ramps).BACK POND

Small outdoor ponds in pots can have other benefits; one made in an unused ceramic planter became a haven for small birds during a summer drought.  They perched on the rounded edge, dined on surface insects and unwary water creatures, and ate most of the duckweed, which is extremely nutritious.

Maintenance and FeedingHay on the Barbie:

When the tank first stabilized, it displayed a moderate population of small copepods.  Over the next two months, the plants grew, the water cleared, and this small ecosystem stabilized and flourished.  However, the population of copepods and protozoa slowly dwindled, and it became apparent that a way to nourish the system over and above the light was needed.HAY ON THE BARBIE Research on nourishing protozoan cultures suggested a hay infusion as the traditional and time-tested method for feeding protozoa, although other grains can be used (  A friend with horses donated a bag of hay.  Two handfuls were placed in a gallon of lake water, the mixture was brought to a boil and simmered for 10 minutes, then allowed to cool.  The infusion was decanted into a clean plastic bottle, stored in the refrigerator, and used to top up the aquarium as needed.  The infusion smelled of fresh hay at first, but after a couple of weeks, even under refrigeration, began to sour.  Aliquots were therefore frozen and thawed as needed.HAY INFUSIONThe effects of adding these nutrients seemed to progress from the bottom of the food chain upwards.  Two days after adding hay infusion, the water clouded and the bacterial count rose.  Over the next few days, the water cleared as the bacterial count dropped, and the number of copepods visibly increased, presumably corresponding to the number of edible protozoan plankton. Repeated use of the infusion during the winter kept up the population of copepods and secondary predators such as hydras; the latter proliferated and could be found in significant numbers in favorite, well-lighted areas on  the glass.INFUSION FRIDGENote also that the infusion should be plainly labelled in the refrigerator.  My wife spent part of a week enjoying my unlabelled hay infusion while I was out of town under the impression that it was herb tea.  It is actually sterile, quite tasty, and probably as nutritious as any vegetable broth.   However, your family will probably be happier if they do not have to second-guess which bottles are consumables and which are culture medium in the refrigerator.

Overfeeding, Heat and Disaster:

We went on a week’s trip, leaving a happy tank filled with hydras, worms, and snails.  We returned to find a dying, smelly tank with moribund plants. The tank had been topped up with hay infusion, then all the windows were closed and the weather turned hot.  Temperatures in the house probably rose to 100 degrees F.  The tank had an oily surface film reflecting lipids from decomposing plant and animal material; this was teeming with bacteria and Paramecia.  It is likely that heat (unlike a lake, pond, or marsh, a small aquarium lacks the cooling reservoir of ground or water, and is very susceptible to overheating), together with overfeeding and bacterial overgrowth (leading to bacteria consuming oxygen) in the warm temperatures produced a killing combination.

Solution:  The aquarium is situated near a window which is closed only during cold temperatures.  A small fan situated on the windowsill blows outside air continually past the tank.  During winter, when our house is kept cold (64-66 degrees F), evaporation is mild, and fresh hay infusion made with boiled lake water can be used to top up the tank, serving the dual purpose of nutrition and evaporation replacement.  In summer when the house, which does not have air conditioning, becomes warm, evaporation is much greater and is replaced with fresh lake or creek water supplemented with lesser amounts of hay infusion.  The best balance of infusion and lake water is still unclear.

Note:  A similar oily sheen is sometime seen on marshes.  The following site explains its origin:

Pests and Problems:

Like any garden, one has to deal with pests.  Having plants grow indoors in the moist environment above an aquarium’s surface is a challenge.  Such plants are exposed to a variety of airborne garden and household infestations that are not as much of a problem with purely aquatic plants, or outdoors plants with freer access to breezes and sunlight.

Watercress and Pond Weed
Watercress and Pond Weed

All houses in the damp Pacific Northwest deal with window condensation to some extent, and black windowsill mold requires regular cleaning.  This mold was a problem with the first tank after it was initially covered, and never quite went away.  It decimated a lovely planting of watercress.  After the collapse of the first aquarium, the second one was left open from the start and never developed this problem.

Black Window Mold

The main problem with the surface plants of both aquaria was aphids; these moved in from the outside garden after about two months and drained the juices from the leaves and stems of the broad-leaved plants, leaving the tougher Equisetum and grasses alone.  Since one cannot spray over the surface of the water, they were reasonably successfully managed by brushing them off every few days with a soft-bristled makeup brush.

Garden Aphids - just waiting to move inside
Garden Aphids – just waiting to move inside.  4X Nikon objective on cell phone, final magnification ~10X

Even though the aquarium is by a window, getting enough light for some of the plants, especially the grasses, is a challenge. The office lamp is left on 12 hours a day; with a fluorescent or LED bulb, heat is not a problem, and energy consumption is low.  Still, some of the plants grow longer stems in response to light levels that are lower than outside sunlight.


Microbus.  ” Collecting and culturing protozoans.”

University of Oregon Materials Science.  “Microbes from a Hay Infusion.”

The Desk Aquarium: How to House Your Leech in Style

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s