No chlorinator line
Selecting freshwater removes the chlorinator, the acid feeder and the associated plant, and adds the planted margin, the graded shelf and its retaining toe, the sand and gravel beds and the planting.
A swimming pond has no chlorinator. The regeneration zone is not a second pond behind a wall: it is a planted margin on the edge of the same water, where clear swim depth grades up a gravel shelf into the planting. A low-head pump turns the whole volume slowly through that bed and the plant roots. True Point sizes the margin off the swim area, draws the blended edge, and steps the safety barrier out around the whole water body.
A plan tells a builder what to set out. It does not tell a client what they are buying. This is the same water body drawn in elevation looking along the length: sand and clear water at the swim end, the bottom rising on a gravel batter through the middle, and the planted margin reading green-brown where that batter runs out. There is no line where one stops and the other starts. The surrounds are what an Australian garden actually puts around a pond, and everything is labelled, because it still has to be specified.
A natural pool has no chemical residual, so the only thing standing between a swimmer and a green pond is biological capacity. That capacity is surface area of planted, oxygenated substrate. The convention is to size the regeneration margin as a fraction of the swim area rather than as a fixed number, because the nutrient load scales with the water body and with how much leaf litter and bather load the swim zone collects. Fifty per cent is the workable Australian default. Drop below forty and the pond swings green in the first warm week after a rain event; go past eighty and you are maintaining a wetland with a lap lane in it.
The zones are not walled apart. The regeneration zone sits on the edge of the pool and blends into it: the sand bottom rises on a graded gravel batter, roughly one in four, until it breaks the planting line, and the water carries across that grade without a face to stop it. What holds the planting substrate in place is not a dividing wall but a submerged retaining toe, a low kerb at the bottom of the batter that stops the gravel bed slumping down into swim depth. Water passes over it continuously along the whole edge, so there is no slot to block and no dead corner behind a wall. Swimmers get a sand bottom that shallows before it plants; the plants get a stable shelf at their own level.
That has a consequence the barrier has to answer for. Because the planted margin is part of the same water body rather than a garden feature beside it, the AS 1926.1 barrier has to enclose the margin too. The fence line steps out past the outer edge of the planting rather than hugging the swim zone, and the run gets correspondingly longer. It is not a detail to leave to the fencer at the end: it changes the lineal metres, and the estimate moves with it.
The sand is not decoration. Washed river sand over a compacted base gives a fine, high surface area medium that supports the biofilm doing the nitrification, and it lets the bottom be raked and vacuumed without tearing up liner or grout. Coarse gravel would look the part but has a fraction of the specific surface and traps debris in voids you cannot reach. The gravel transition band around the perimeter is the working compromise: it takes the abrasion where feet and equipment land, and it stops sand migrating up the batter into the skimmer line.
Depth matters both ways. Too shallow and there is not enough medium to carry the biofilm through a heavy week. Too deep and the lower layer goes anaerobic, which is the smell people associate with ponds and never with a well-built one. Two hundred and fifty millimetres is the sweet spot for the volumes we build.
A chlorinated pool pushes water fast through a pressure filter and needs pressure to do it. A natural pool does the opposite: it moves a large volume slowly through a bed that is barely above the water line, so the duty point is high flow at very low head, typically two to four metres. A conventional pool pump run at that duty is working off the wrong end of its curve, wasting most of its input as heat and, worse, driving flow fast enough to scour the biofilm off the substrate. A purpose-built low-head unit at half a kilowatt turns the whole body over in twelve hours on less energy than a bar fridge, and the slow pass is what the biology actually wants.
The species mix is drawn from plants that suit local conditions rather than from a European pond catalogue. Typha orientalis, the cumbungi or bull rush, is the workhorse emergent and the tallest thing in the bed. Phragmites australis, common reed, is native here and does the bulk of the nutrient stripping. Baumea articulata and Baumea rubiginosa are jointed twig rushes that hold the middle shelf. Carex appressa, tall sedge, and Juncus usitatus fill the margin with fine foliage. Under a subtropical mix the Typha gives ground to Schoenoplectus validus and the marginals shift to species that hold through a wet summer.
Vigour is the thing to watch. Typha and Phragmites are both capable of taking a bed over, which is why the low vigour mix exists: it swaps them out for Baumea and Carex, plants at higher density to compensate for the smaller individual footprint, and trades a little peak capacity for a bed that does not need thinning every second season.
Selecting freshwater removes the chlorinator, the acid feeder and the associated plant, and adds the planted margin, the graded shelf and its retaining toe, the sand and gravel beds and the planting.
Swim area, regeneration area, water volume, plant count and pump duty are all read off the drawn geometry. Change the ratio and every figure and the bed itself move together.
A swimming pond is a swimming pool under AS 1926.1. The planted margin is part of the water body, so the barrier is set out from its outer edge and the run is longer than for the swim zone alone.