BALI, the British Association of Landscape Industries, is the trade body for the UK landscaping sector. Membership is not automatic; it requires meeting standards the association sets for the industry, and it signals that a business operates within a recognised professional framework rather than entirely outside one. When speaking to a designer, a fair question is simply whether they hold BALI membership and what that membership has required of them.

Planting does most of the biological work in a natural swimming pond, but it rarely works alone. Two further elements, UV treatment and pumped circulation, sit alongside the planted regeneration zone in a well-designed chemical-free pond, and understanding what each one does helps explain why the combination holds up rather than the planting on its own.

Algae, the thing every pond owner is actually trying to manage, needs nutrients to grow, principally nitrogen and phosphorus, along with sunlight and warmth. A chemical pool deals with algae directly, by making the water hostile to anything living in it. A well-designed natural swim pond takes a different route: it competes algae out of the nutrients it needs, using plants that are deliberately chosen and positioned to take up those same nutrients faster and more persistently than algae can. Marginal plants at the water's edge and submerged plants within the water column between them cover most of the routes nutrients enter a pond, from surface run-off to material breaking down within the water itself.

A pond, and particularly a swim pond, is a considered purchase most homeowners make once. There is no easy way to test-drive a designer before committing, which is why credentials tend to carry more weight in this kind of decision than they might for a smaller, lower-stakes purchase. Three accreditations worth understanding, and worth asking any designer about directly, are BALI membership, CHAS accreditation and ISO 14001.

The regeneration zone is not a static feature once planted. Plant density, species mix and the proportion of the total pond given over to planting all affect how well the zone performs its job, which is why the balance is designed rather than left to chance. A regeneration zone that is too small for the size of the swimming zone will struggle to keep pace with nutrient load, particularly once a pond is established and in regular use, so getting that ratio right at the design stage matters more than almost any other single decision in the build.

It is worth being deliberate about what not to lean on too heavily. A specific count of completed projects, a claimed number of years trading, or a stated service radius are all figures that are easy to present persuasively and hard for a homeowner to verify independently. None of those figures tells you whether a design will suit your specific garden. Credentials such as trade body membership, health and safety accreditation and environmental standards are more concretely checkable, and a portfolio's actual content, the variety, the explanation, the evident care in planting choices, Michael Wheat Ponds tells you more about fit than any single number.