we have an above ground unused Fish pond 3’ deep. If make it into a garden I need to drill holes to let the water drain out. At what height do I drill the holes so that I can use the rain water and not drown the plants.
Thank you for your query.
From the image, your brick-sided fish pond is a very attractive feature which would look wonderful as a garden. It is not mentioned whether the pond was successfully used for fish but it is expected that there is some sort of liner. Adequate drainage is essential for plant health. Since accessing the bottom of the fish pond/planter is not possible, drainage holes need to be positioned low enough in the side to prevent water pooling in the bottom of the planter. Good drainage is necessary to avoid excess moisture at the roots preventing root rot. For more details, please click on the link, Old Brick Planter.
There are several additional issues to consider. Once the liner of the pond is breached, water seepage may cause degradation of the masonry. The winter freeze/thaw cycle can also damage the brick and masonry. The depth of the planter will need to be decreased to not more than 60 cm (2 feet) deep as the weight of the increased soil depth can compress the lower soil layer resulting in poor drainage. Other gardening considerations are the choice of fast draining soil mix and plant choice. Many plants grow satisfactorily in a soil depth of up to 30 cm (12 inches).
As converting your brick fish pond to a garden is a complex project, it is suggested that you consult a local business with experience with retaining walls, or a member of Landscape Ontario.
For further information, please click on the following links:
Wishing you all the best in converting your fish pond to a garden.