Not a lot at all, definitely not 50% of the swimming space
You might be under the impression you need a lot of additional space for the marginal plants. This area is a shallow shelf filled with nutrient absorbs aquatic plants. When swimponds were first conceptualised in Germany in the 80s, the designers only used plants to keep the water nutrients balanced and did not add any equipment.
Mechanical and Biological fresh water filtration technology has come a long way. Along with a submersed circulatory pump, the filtration unit with UV Bulbs does all the heavy lifting on keeping the water moving and take care of the water clarification.
We use a combination of plants and filtration on our projects. This means we aren’t relying on a single method of water purification which can be at a higher risk of water clarity issues (as it is more complex to maintain)
Relying solely on plants, you’d need serious consideration of the plant maintenance schedule. This is a hassle a lot of our clients do not want or need. With our hybrid design approach, there is less worry and less maintenance
There is no wasted space used up by huge planted shallow shelves that you can not actually swim in. Its great news for clients or architects with more compact spaces. Filtration can be over specified to reduce the amount of plants down to a very minimal level which is mostly a decorative design feature.
If you already have a chlorinated swimming pool, it is possible to swap the chlorine system for a fresh water alternative and the planting area can be designed to be added on shallow shelves inside the existing pool footprint.