That pond would be great for breeding fish or growing up fry. If it was higher, say 2 or 3 feet high, it would be ideal but even at 18 inches high, it would make a good breeding/ rearing pond for most fish.
Most ponds are only 18 inches high for safety reasons, if a child falls in there is less chance of them drowning. However, you can drown in 2 inches of water if you are face down.
If you get a pond like that, put a plastic screen over it to stop birds and other animals getting the fish. Attach the screen firmly and it should stop people getting in too.
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You can use any aquarium plants in ponds. Water lilies do well and so do Amazon sword plants. Vallis, Hygrophila species, Ambulia, Ludwigia, and most other aquarium plants will thrive outdoors in a pond.
GROWING PLANTS IN POTS
We use to grow plants in 1 or 2 litre plastic icecream containers. You put an inch of gravel in the bottom of the container, then spread a thin layer of granulated garden fertiliser over the gravel. Put a 1/4inch (6mm) thick layer of red/ orange clay over the fertiliser. Dry the clay first and crush it into a powder. Then cover that with more gravel.
You put the plants in the gravel and as they grow, their roots hit the clay and fertiliser and they take off and go nuts. The clay stops the fertiliser leaching into the water.
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TRUE AQUATIC VS MARSH/ TERRESTRIAL PLANTS
Lots of plants are sold as aquarium plants and most are marsh plants that do really well when their roots are in water and the rest of the plant is above water. Some marsh plants will do well underwater too.
Hair grass is not a true aquatic plant, neither is Anubias.
Some common marsh plants include Amazon sword plants, Cryptocorynes, Hygrophila sp, Rotala sp, Ludwigia sp, Bacopa sp. These plant do reasonably well underwater.
True aquatic plants include Ambulia, Cabomba, Hornwort, Elodia, Hydrilla and Vallis.
The main difference between marsh plants and true aquatic plants is the stem. True aquatics have a soft flexible stem with air bubbles in it. These bubbles help the plant float and remain buoyant in the water column.
Marsh plants have a rigid stem and these plants can remain standing upright when removed from water. Whereas true aquatic plants will fall over/ collapse when removed from water.
Marsh plants do best when put on stands in ponds so the roots are wet but the leaves are above the water. You can use milk crates or bricks to put the pots on so the leaves can come out of the water. Or you can cut a hole in some polystyrene foam and put the plant in the hole. then let the plant float around the pond. The foam keeps the leaves above water and the roots stay in the water.