This pond was built in December 2007 in the earlier days of my turn-the-front-lawn-into-garden project.
The tires came from a park mowing tractor so are wider than normal tractor tires, giving extra height to the pond. You can usually pick these up free, in New Zealand anyway, from large tire repair and supply workshops: mine came from the parks maintenance company I work for - free disposal for them and free supply for me!
two tractor tires (one, two, tractor, car - your choice)
large cardboard box, old carpet, etc
thick polythene sheet from a local BORG (Big Orange Retail Giant)
flexible drainage coil (I had this lying around)
geotextile (eg weedmat, mudstop, etc) [oh, or you could use old carpet!]
soil, container mix, or compost
water plants and land plants
two terracotta pots
reciprocating saw, jigsaw, hacksaw or even a sharp sturdy knife
short length of 25mm PVC pipe
Step 1: Cut sidewalls from tires
Cut one sidewall from one tire and both walls from the other, leaving about a 75mm (3 inch) lip. I only cut out the upper wall of the second tire at first, but the polythene would not mould around the convoluted 3D-ness of this arrangement. Unfortunately, I did not take photos of the second try, but you'll get the idea.
Smaller tires can be done with a jigsaw or even a small knife: see the paring knife I used on car tires (thanks for the use Sweetie ... oh, I thought I'd asked you about that?... oh ... er ...).
Step 2: Lay first tire
Lay the first tire complete sidewall down on the flattened cardboard box to help protect against sharp things.
Fill the hole with sand until it is level with the lip of the bottom rim.
Thickly layer newspaper over the bottom and up the sides as best you can (damp paper sticks to the wall better).
Step 3: Add second tire
Make sure the tire is sitting firmly.
Step 4: Insert polythene lining
Insert the polythene so that a roughly even amount is poking out the top all around. To estimate the size of the plastic, I had run a string progessively down one inside wall of the pond, around the bends, across the floor and up the other side, then added 300mm (12 inches) for safety.
Fill the pond to about 3/4 up the second tire. The polythene will look terribly crumpled, but that's life.
Step 5: Clip polythene to lip with drainage pipe
Press it over the pond lip, trapping the polythene, then apply a clamp (or preferably use a helper; dogs do not qualify). Using a clamp or two to hold the polythene until you get to it can help.
Insert the PVC pipe to keep the slit open and work your way around the tire applying more clamps or helpers as you go.
When you get to the end, match up the two pipe ends and cut the last one to length.
Use a sharp knife to trim the excess plastic. I should have filled the pond further than I did, but fortunately there was enough slack for the polythene not to pull out of the drainage pipe when I did fill the pond.
Step 6: Voila! Pond. Add plants and fish
Boy, this was a proud moment!
To raise the aquatic plant to a more appropriate depth, I used a large upside-down terracotta pot.
About 6 weeks of summer later near the end of Jan 08, the pond was a going concern with happy fishes. All summer I used the water to water the vegetables: fish wastes are fertiliser. As the garden took most of the pond, the water is regularly topped up with fresh water. Because of this I have not needed to filter the water. Algal growth was a problem until I allowed Azolla to cover the surface, thus cutting down the light.
As the garden got bigger, I built a pumped system to empty the pond, but that's another story.
Step 7: Add soil retaining fence
Use highschool geometry to estimate the length of mesh or do like me and just wrap it around the pond with a bit of overlap until it looks about right. Allow for 100 - 200mm (4 - 8 inches) between the pond and the mesh.
Staple the geo-textile on to the mesh to hold it in place while erecting the fence. I left a space at the top for plants to climb on, but should not have as the textile has dragged down over the months and is now too low.
Pin the ends of the mesh together with a doubled-over length of fencing wire (New Zealand's famous No. 8 wire is perfect for this! Look this up: it epitomises the Instructables philosophy also).
Carefully fill the resulting space with soil, watering it down as you go. In the photo, my geotextile wasn't high enough so I couldn't fill it right up.
Plant the top, and/or cut slits in the side (at the top of a mesh square to allow for downward creep of the texile) to insert cuttings or divisions. I started with begonias and herbs.
Step 8: Pond updates
This is my first 'able, though I've been a member for ages. Positive feedback and constructive criticism are welcome.
Here are some additions from my responses to readers' comments:
A couple of car tyres (to use the correct spelling... ;] ) would do as a small pond, and would be easy to move once empty (especially if it was on a sheet of ply or a pallet, and the soil step was foregone). A rule of thumb, I understand, is to have the most water possible per fish, otherwise you'd need filters and aerators, etc. If you did not put the soil around it, you may have to paint it white or shade it in summer (and then you could take the shade away in winter so the tyres warm up and stop the pond from freezing!).
I've seen a lot of those YouTubes, Instructables, etc on turning tyres inside out: if you look closely in photo 1 you can see where I tried this for the top tyre of the planter behind the pond with the banana palms in. Personally I don't do this because: I don't like the look, I don't gain enough in volume to warrant the effort (in fact I'd say I get less, but I haven't quantified that), I always leave the bottom sidewall on to help with water retention during summer (also helps keep the soil in if I have to drag the planter anywhere), and can you even IMAGINE doing that with tractor tyres??!!!
I have thought about syphons and pumps etc, but I used to just use a watering can and scoop the water out. This was OK while the garden was small, but last summer (NZ is now in winter), I got our old swimming pool pump from storage (... NEVER throw anything out ...), bought fittings from the BORG, and started using that. It has the added benefit of sucking out the detritus from the bottom. Earlier on I had to siphon the entire pond out to get the crud and refill it totally. I might get organised next summer and set up an aquaculture system, with the ability to divert the water to a hose for the garden.
Step 9: Get published in a gardening magazine! :]