Alasdair "Ali" Mackenzie grew up around ponds in Scotland and spent more than 25 years in the British military. In the summer of 2023 he took on Arizona caliche, desert soil cemented so hard it stops a shovel, in heat that reached 112 degrees. What he built north of Phoenix is a raised koi pond, five feet deep at its deepest, with two aerated bottom drains, a GC Tek WattMizer PLUS PRO filtration system and 16 koi. Every one of them has a name. The biggest is called The Bruce.
We rebuilt Ali's pond in 3D in our Pond Planner, pergola and all. Skip ahead to explore it.
From a garden center in Scotland to the Arizona desert
"I grew up around ponds. My mum and dad own a garden center. Had the goldfish pond in the backyard, you know. I was always fascinated by that, running water, seeing fish."
Ali's first pond was a small one, with no bottom drains and no return jets. Years later, at a rental near Phoenix, he built a bigger one: about 1,700 gallons and four feet deep, stocked with 20 koi he bought in 2021 at three to ten inches long. It ran for more than two years with crystal clear water. Those early ponds also taught him what he would change.
"I didn't have bottom drains. I didn't have return jets... I didn't make the pond big enough!"
In 2023 Ali and his wife moved to a house with a bigger yard, and he wanted as many of his koi as possible to make the move with them. This would be the last pond he built, so it had to have everything.
"I'm now going to build a pond that's going to be a forever home. It needs to be big enough... I want bottom drains. I want return jets. I want two types of filtration on it. Everything I thought about as the years went past."
Planning the build with Derek
In June 2023 Ali sent his plan to Derek on our team: a rectangle 16 feet long and 9 feet wide, dug two or three feet into the ground with a concrete block wall about two feet above it. That gives four to five feet of water without digging a five-foot hole. He had a lot of questions, and he apologized for them.
"Sorry for still pestering you with questions, but I want this to be my final build and want it spot on."
Derek's answers set up the whole system:
- Two 4-inch Aquadyne Rhino II bottom drains, each with a built-in air diffuser. One drain pulls waste from about a six-foot radius, so a pair covers a 16-foot floor.
- A separate 4-inch line from each drain, kept at 4 inches up to pond level and reduced to 2 inches at the filter. Keeping the big pipe below the waterline leaves room to switch to gravity-fed filtration later.
- A WattMizer PLUS PRO 6.0, which comes with two AquaSieve2 prefilters, so each drain line gets its own sieve.
- Three tangential pond returns, each on its own valve, angled to turn the water in a slow circle toward the drains, with one aimed at the skimmer.
Ali placed his order on June 13, 2023.
Digging through caliche at 112 degrees
Every pond build has a villain. Ali's was caliche, a desert subsoil that calcium carbonate cements into something closer to rock than dirt.
"The biggest challenge was the ground here in Arizona. You're practically pickaxing away to get through it for hours on end... I only got a couple of inches!"
A friend brought an excavator, and Ali did the rest with a rock pick-axe in heat between 100 and 112 degrees. He stopped about three feet down and built the walls up from there in concrete block. He set both bottom drains in concrete, cushioned the hole with old carpet and underlay he collected from neighbors, and laid the rubber liner on top. Looking back, he calls it "an absolute beast of a build in the Arizona ground."
The part he enjoyed most surprised him: the plumbing.
"I really enjoyed doing things like the bottom drains, the return jet outlets... And that first cut, when you put a Stanley knife onto that rubber, you're thinking, 'Geez, I'm going to put thousands of gallons of water on top of this and is it going to hold?'"
It held. The first time the three returns pushed water back into the pond without a single leak, he says, was pure satisfaction.
A 435-pound delivery
GC Tek builds each WattMizer system at its factory and numbers every union, then takes it apart into labeled sections and ships it by freight. Ali's arrived in July.
"My wife just informed me that a pallet carrying truck pulled up at the house with a delivery weighing in the region of 435lb! They did not have a fork lift to remove it and plan to come back tomorrow!"
By mid-September he wrote to us: "Filtration system all set up now and slowly working on the remaining pipework. Really happy with it all so far."
Ali didn't rush any of it. His koi spent about six months in a filtered swimming pool in his garage while he built, and by December 2023 the pond was full and the fish were home, swimming behind bare block walls.
December 2023: filled, fish in, and the stucco still to come.
How Ali's pond stays clear
Ali wanted two types of filtration, and the pond runs on two separate circuits.
The bottom drain circuit does the heavy work. Both drains pull water off the floor through their own 4-inch lines to the WattMizer PLUS PRO 6.0, which sits on a pad by the yard wall about 25 to 30 feet from the pond. Each line runs through its own AquaSieve2, which screens out solids first. The system's Performance Pro pump then pushes the water through an AlphaNANO bead filter, which traps fine particles and holds the bacteria that break down fish waste, and through a ZapPRO high-output UV clarifier, which clears the free-floating algae that turns water green. The water comes home through the three tangential returns. Swing check valves on the intakes keep the pump primed while Ali backwashes the bead filter.
A Hakko 80LH air pump feeds a Matala manifold, which sends air down to the diffusers built into both drains, so oxygen goes in at the deepest point of the pond.
The surface circuit is separate. A 10-inch Blue Thumb Elite skimmer on one side pulls leaves and floating debris off the top, and its own pump sends that water to a 30-inch Blue Thumb Elite waterfall filter at the back of the pond. The waterfall box holds biological media, and the water spills out over rocks and a tipped terracotta pot.
"The waterfall is going to work solely with the skimmer pump. So my returns from the filtration unit will be via TPR."
Potted plants add a third layer. Blue flag iris, Louisiana iris, red-stemmed sagittaria, Flamingo water celery and hardy water lilies all take up the nitrates the bacteria leave behind.
Planning a system like this? Our buyer's guides cover bottom drains, bead filters and UV clarifiers, with sizing and installation tips.
Built for the desert
An Arizona summer means hard sun, warm water and fast evaporation. An open timber pergola with a shade cloth stands over Ali's whole pond, so the koi have shade through the hottest hours. A Blue Thumb automatic fill valve tops the pond up from his well as the dry air takes water out. The walls rise about two feet above the gravel yard, finished in stucco the same color as the yard walls and capped in red brick.
Sixteen koi, all with names
Ask Ali why koi and he doesn't hesitate.
"I can sit out by the koi pond and the fish gracefully move in a different way... I just find it so relaxing."
The end of his day belongs to the pond. "My decompressed time... will then be just sat at the pond. It's a ritual." The koi meet him there. They "come up to you like little dogs, you know, and they just sit there. There's a connection there."
Ali has 16 koi, and what surprised him most was how different their personalities are. The biggest is The Bruce, named for Robert the Bruce, King of Scots. When the summer heat peaks, The Bruce sulks in the shade.
"He was looking at you... I'm telling you, he's not happy with this weather, big man. You'd be better off in Scotland."
When the temperature drops, he's back. "The Bruce is out there! He's the first over to feed... back to his old self!" A small butterfly koi is the opposite and loves the heat. At feeding time the whole group shoots across the pond in a bow wave. Ali also runs a power jet on a timer as a "koi trainer," a current that keeps his fish swimming and strong.
Ali's advice for your first koi pond
Here's what the "Husband in the Hole," as Ali puts it, would tell anyone about to dig one.
Don't undercut on size
"If it's going to be your forever pond... don't undercut on size." Koi keep growing, and running out of room in his last pond is why this one is bigger.
Put in bottom drains
"If you're going to do koi, put in bottom drains. Use them all the time. Don't skimp..."
Don't rush it
Set a clear timeline and give the fish somewhere safe while you build. Ali's koi waited out the build in the garage pool.
Get your hands dirty
"If they're on the fence, then they're not ready... Get your hands dirty. Get in among it. Know what's in the ground. Know where your pipes are." Doing the work himself is a big part of why the pond means so much to him.
Finishing touches
Since the bare-block days of December 2023, the walls have been stuccoed and capped in brick and the pergola has gone up. In late 2025 Ali added a brick paver seating area against the pond wall and a Buddha statue beside the waterfall.
When the first version of this story went live in December 2025, Ali sent us a message: "You have certainly made an old girls day back home in Scotland. Mum and Dad delighted with it."
Ali's pond at a glance
- Built by: Alasdair "Ali" Mackenzie, with system design help from Derek at Play It Koi
- Location: north of Phoenix, Arizona
- Build: do-it-yourself, June to December 2023, with the stucco, pergola and seating area added later
- Shape: a rectangle, planned at 16 by 9 feet, with a rock planter built into one end
- Construction: dug about 3 feet into caliche, with a concrete block wall about 2 feet above ground, finished in stucco with brick coping
- Depth: 5 feet at the deepest
- Volume: roughly 5,000 gallons
- Fish: 16 koi, all named
- Filtration: two aerated bottom drains, two sieves, a bead filter and UV on one circuit; a skimmer and waterfall filter on the other; potted marginal plants
- Water features: a waterfall and three tangential returns
Ali's equipment
All of this came from Play It Koi:
- Aquadyne Rhino II bottom drains, 4-inch with built-in air diffusers (two)
- GC Tek WattMizer PLUS PRO 6.0 system with AlphaNANO media, rated for ponds up to 17,000 gallons. It includes two AquaSieve2 prefilters, a Performance Pro pump, an AlphaNANO bead filter and, on Ali's 2023 system, a ZapPRO high-output UV clarifier. New systems ship with the NishikigoiUV-HD160 instead.
- Tangential pond returns (TPR), 1-1/2 inch (three)
- Blue Thumb Elite pond kit, 21 by 26 feet (7,800 GPH), with a 10-inch Elite skimmer, a 30-inch Elite waterfall filter, the pump, a 25 by 30 foot rubber liner and underlayment
- Hakko 80LH air pump with a Matala heavy-duty 3-valve air manifold
- GC Tek ElekTrik pole control center
- Blue Thumb automatic water fill kit
- Valterra 2-inch gate valves and flexible PVC pond hose in 2, 1-1/2 and 1/2 inch
- Plants: blue flag iris, Louisiana iris 'Clyde Redmond', red-stemmed sagittaria, 'Flamingo' water celery and 'Attraction' red hardy lilies. See our pond plant buyer's guide for more koi-proof picks.
- Koi: a Gosanke koi package
- Food and water care: Nijikawa Growth koi food, Koi Pharma Koi Defender and Evolution Aqua Pure Sludge Bomb
Plan a pond like Ali's
Now you can walk around Ali's pond yourself. We rebuilt it in our Pond Planner from his plans, his emails with Derek and his photos: a 16 by 9 foot rectangle dug 3 feet down, with a 2-foot concrete block wall above ground finished in stucco. Both aerated Rhino II bottom drains sit on the center line, the 10-inch Blue Thumb Elite skimmer is in the end wall, three tangential returns turn the water, and the 30-inch Elite waterfall filter spills in at the back. The WattMizer PLUS PRO 6.0 and the Hakko air pump sit on a pad off the end of the pond, and a timber pergola shades the whole pond.
The planner keeps the water 6 inches below the coping, so the plan holds 4.5 feet of water and about 4,850 gallons, close to the roughly 5,000 Ali built. The pergola is hidden in the 2D plan so you can see the plumbing, and two Adirondack chairs on a stone patio stand in for his brick paver seating area. One difference: the planner runs the skimmer and waterfall through the same pump and filter as the bottom drains, where Ali gave his skimmer its own pump that feeds only the waterfall.
Open Ali's pond in the planner to spin it around in 3D, watch the air rise from the drains and see every part on the list. Like what you see? Hit "Start my own pond" and design yours.