You need a pond. Or a ditch. It doesn’t have to be a big one. Even a small one will be a valuable resource for frogs and toads. It should have areas with sloping sides or, if you use an old sink or similar, just a ramp so that the frogs can climb out when they grow out of being tadpoles. Also it needs plenty of places for them to hide. If it dries out in high summer, that doesn’t matter that much. The pond is needed for spawn in spring. Ideally it needs a shallow end for them to spawn in and build it away from trees. Instructions for making a wildlife pond can be found here. To get some other wildlife, take a jam jar to the nearest slow moving river or pond and scoop up some of the bottom silt. That will give you water fleas, caddis, dragonflies and perhaps fresh water shrimp.
In many places frogs or toads will just turn up. Do not ever take spawn from the wild and put it in your pond: nowadays they say do not even take some from from a neighbour’s garden pond. There are now two frog diseases and you might be spreading it. However if you are putting a pond in a completely walled garden, or if no amphibians have turned up after 2 or 3 years, consult your local wildlife trust. They may be able to help if they know of a pond that is going to be drained or dried out.
Don’t put goldfish or koi or any kind of fish in the pond. They will eat the tadpoles. Don’t be in a hurry to put in water plants because you need to make sure you are putting in native plants. People with ponds will offer you plants. Check first. Garden centres are not reliable sources of information. Also anything you buy in a garden centre may have duckweed or some other invasive weed with it, so do an amazingly thorough check before putting it in the pond. I got various native species from the local pond, just taking a small amount. But even there be careful: some rivers and ponds are infested with foreign invading plants.
GOOD PLANTS: are hornwort (Ceratophyllum Demersum), water milfoil (Myriophyllum spicatum) and similar, any of the native pondweeds. There’s also an underwater crowfoot (Rananculus aaquatili), Curled pondweed (Potamogeton crispus), water-starwort (Callitriche spp), water-violet (Hottonia palustris) and willow moss (Fontinalis antipyretica). For floating plants try broad-leaved pondweed (Potamogeton natans), fringed waterlily (Nymphaea peltata) and yellow waterlily (Nuphar lutea). These last two are pretty dominating so you may have to pull a lot out each autumn to keep them under control.
BAD PLANTS: Beware of garden centres. Most of them have no idea what they are selling. Most sell invasive non-native plants like Canadian waterweed (Elodea Canadensis) or Esthwaite waterweed (Elodea nuttali). Other plants to avoid are water fern (Azolla filiculoides), Water primrose (Ludwigia granfiflora) New Zealand pygmy weed (Crassula helmsii), parrot’s feather (Myriphyllum aquaticum), and Curly pondweed (Lagarosiphon major). If these get into your pond, take every single little bit out by hand and warn the garden centre about them. Do not put them down a drain or in the rubbish. Burn them or bury them. They are dangerous invaders.
Duckweed is invasive too and often comes along with bought plants like water lilies. It may be worth picking out every single bit of it (should you get any) so that the pond looks better but frogs actually like it and I have seen tadpoles eating it. Check what kind you have. The worst is the least duckweed (Lemna minuta), an alien species. But there are three kinds of rare duckweed which are interesting – rootless duckweed (Wolffia arrhiza), fat duckweed (Lemna gibba) or great duckweed (Spirodela polyrrhiza). If you’ve got these kinds, tell your local wildlife trust. But you are most likely just to have common duckweed (Lemna minor).
Margin plants which are useful incude water mint (a bit invasive!), water forget-me-not (also a bit invasive!), articulated rush, common spike rush, watercress, fool’s watercress (don’t eat it!), marsh pennywort, marsh marigold, purple loosestrife, marsh woundwort, sedges like carex pendula, ivy-leaved crowfoot, and ragged robin. Bulrushes are too large and invasive for garden ponds. Yellow iris is also invasive but they look so great it may be worth planting them and cutting them back each year.
Blanket weed of filamentous algae looks bad but a little amount is quite good for pond animals. It usually results from pollution – fertiliser run-off form agricultural land or tap water.. Water quality can be improved by barley straw in nets, sold by garden centres. Fallen branches, particularly willow, also reduce algae.
The surroundings of the pond matter too. Long grass should be directly around the pond for the new tiny frogs and toads to hide in. Let the grass to grow right into the pond covering the sides. (This will protect the rubber liner). Toads and frogs need places to hibernate so think about building a log pile or a stone pile near the ponds.
In autumn, don’t put an ordinary net down. If you must have a net, raise netting up on rocks or sticks so that the frogs can get into the pond under it. Stapling the net to broom handles and placing the other end in the earth might do the trick. Or if your pond is too large for this, use a net held up by Gro Thru frame head legs – normally used to keep plants upright. You can find these in garden centres. Fiddle around till you have fixed the net on the top of the head, rather than letting it slip all the way down.