You'll see it. Here's exactly how much.

It sits 77mm above the rim and reaches 65mm back over the tank. The home page has photographs taken in normal light, not in a studio, in both black and white. If a completely clean rim is non-negotiable for you, this isn't the product for you.

It isn't silent, but no, it's certainly not noisy.

There's a mild hum at full speed, but no whine — the motor runs in a quiet stepping mode — the carriage travelling on its bearing makes a soft mechanical sound, and the cover carries some of that along the length of the sweep.

At its slowest speed, however, it is truly "silent"

There's a clip on the home page, recorded in a quiet room with the tank running, so you can hear exactly what it does before you decide. If it turns out to be more than you want in a bedroom or a home office, you have 14 days from delivery to send it back.

Yes, and most people should. One thing is worth knowing: your pump is now on a moving arm rather than fixed to the glass, so how it changes thrust matters more than it used to.

Start with a smooth wave mode — sine or similar — at the lower end of its rate range. Those ramp the thrust up and down, and the arm carries that comfortably. Sharp on-off modes change thrust instantly, and an instant change is what moves the arm rather than the water.

The check is just to look at it. The arm should sit steady while the carriage travels. If it's visibly nodding, in order: lower the wave rate, then switch to a smoother mode, then shorten the arm extension if your aquascape allows. Any one of the three usually settles it inside a minute.

Yes - Fusion Flow is UKCA and CE Marked. That work covers electromagnetic compatibility and RoHS requirements.

No, and it doesn't have one. There's one button, one speed dial and a status LED.

Tap the button to pause, hold it to teach the sweep — switch the motor off, push the carriage to each end, done. No account, no pairing, no firmware server to be quietly discontinued in three years. If app control is a dealbreaker I understand, but this was a decision, not an omission.

When power comes back, it re-homes itself and resumes the same sweep you taught it. The positions are stored in flash, not in volatile memory. You don't have to do anything.

It means every one is made to order rather than pulled out of a mould, and there are two consequences worth knowing before you buy.

The good one: your colour costs nothing extra, a design revision reaches you in weeks instead of a tooling cycle, and a replacement part is a print rather than a minimum order of five hundred. At the numbers I build at, injection moulding would cost more than this product will ever make. Printing is the reason it exists at all.

The honest one: printed PETG carries fine layer lines. They are visible close up, most obvious on curved surfaces, and there is slight variation from one unit to the next. That is the process rather than a fault, and I am not going to photograph it in a way that hides it.

What I do control: no stringing, no warping, no blobs or gouges, and dimensional accuracy where it actually matters — rail alignment, clamp fit, and the sealing geometry around the channel. Anything that fails on those gets reprinted rather than shipped.

The practical version: it lives on the back rim, above the water, and you look at it from across a room. Layer lines at 300 mm are not layer lines at two metres. If a moulded finish is what you are picturing, you have 14 days from delivery to send it back, and I would far rather you did that than keep something you are not happy with.

The firmware is built to prevent it. A parked powerhead blasts one spot continuously and can damage sensitive corals, so "keep moving" is the priority — a control fault degrades to continued motion rather than to a stop. That single rule shaped the whole control design.

What firmware can't prevent is a mechanical failure. There's a belt, a bearing, a motor and a mains adaptor in here, and any of them can fail eventually, the same as in a return pump or a powerhead. So it shouldn't be the only thing moving water in your tank, and it's worth keeping an eye on it the way you would any other piece of equipment.

The moving parts sit inside a sealed housing with a channel beneath the rail that catches wear debris and retains it. The housing is PETG, which is inert; there's no photopolymer resin anywhere in the product. The only things entering your tank are the arm and the pump mount.

Cable is what kills moving equipment, so it's worth being specific.

For a cable that flexes continuously, use a bend radius of at least ten times its diameter—below about five times, copper starts breaking strands. And this moves a lot: on a 430 at speed, a round trip takes roughly 24 seconds, which is over a million round trips a year.

So the cable isn't bent around anything. It's carried in a loose hanging loop that reshapes as the carriage travels, spreading the movement along its length instead of concentrating it in one spot. As fitted, the tightest radius in that loop is about 50 mm — ten times a typical 5 mm powerhead cable.

Two anchor points are at the drive end and two on the carriage, one on each side. Use the pair on the same side as your pump's cable outlet, and keep the loop open the whole way, with no reverse bend and nothing rubbing the rim.

Setting the slack takes ten seconds. Push the carriage to the drive end, where the loop hangs deepest, and check it stays clear of the water — a cable dipping in and out will creep salt along itself. Then push it to the far end and check the cable isn't pulling tight. Anywhere between those two is right.

If your pump's cable is thicker than about 5 mm, give it a little more slack: the number to beat is your own cable's diameter times ten.

The cover overlaps the inner channel, so splash and aerosol have no straight path to the rail, and a drip edge returns condensation to the tank. You'll get some salt on the outside of the housing, as you do on everything above a reef tank — it wipes off.

Less than your skimmer, more than nothing, and I'd rather tell you now than have you find out.

At each water change, about a minute: wipe the housing, check the clamp hasn't moved, and listen to one sweep. A linear bearing tells you it's unhappy long before it stops working.

Every four weeks, about fifteen minutes with the cover off: clear the debris channel, wipe the rail and re-grease it, check the belt tension. The grease is an NSF H1 food-grade synthetic — the same standard used where lubricant might incidentally touch food — and a tube comes with the unit.

Every six months, about half an hour on a bench rather than over the tank: the same again plus a proper look at the belt, the cable and the mount magnets.

The bearing is a replaceable service part rather than something that ends the product's life. How often depends on your pump — see below.

It will need adapting. The arm travels through the space a net occupies, so a single sheet across the whole top and this unit can't both be there.

The fix is to net around the unit rather than over it. Framed cut-to-size kits — Red Sea's DIY Net Cover among them — are made to be built around rim-mounted equipment, so you frame panels either side of where the unit runs. One unit at one end, net the rest. Two units, one at each end, net the middle.

If you keep fish that jump, sort this out before you order rather than after it arrives.

Yes, and on a wide tank it's worth it. Because each unit randomises its own sweep independently, two of them never fall into step (and if they do, they will soon go out of sync) — you get genuinely uncorrelated flow from two moving origins, which is something no arrangement of fixed pumps can produce.

Add a second of the same size and the pair discount comes off automatically at checkout: £29 on the 230, £39 on the 330, £49 on the 430, £59 on the 470. They don't have to be the same size, but the discount only applies if they are.

Yes, and you don't have to tell me why. Cancel any time before it ships and I'll refund you in full, deposit included. Once it arrives you still have 14 days to decide — send it back in the condition it reached you and you get your money back. That's your right under the Consumer Contracts Regulations 2013, and I'd rather say it plainly here than bury it in a policy page.

12 Months. If something fails, email me. It comes back to me, not to a call centre.

Up to four weeks, and usually less. Generally, nothing is pre-built — when your order comes in, I print the housing, assemble components, build the electronics and run the unit for a while before it goes anywhere. You'll hear from me within two working days of ordering with the date I'm working to, and again on the day it ships. If anything slips, you'll hear it before the date, not after.

The way it works is the subject of a UK patent application — GB2619546.1, filed in August 2026. Patent Pending.

The way it looks is protected now. Seven UK registered designs, numbers 6548662 to 6548668, registered in August 2026 — covering the complete apparatus, the housing, the support arm, the clamp and the pump mount separately. Those are granted and in force, not pending.

EU and North America : please contact me first. Overseas orders ship with a PSU appropriate to the destination.