AI Prime Flex Arm 18 in — Flexible Silicone Arm for Deep Aquariums - AquaIllumination

The AI Prime Flex Arm 18in. is the long version of AquaIllumination's flex arm. Same idea as the 12in., but six inches more — which is what makes the difference when you're lighting a deep tank or a sump. AquaIllumination describes it as their most flexible mount for a rimmed or rimless tank.

The light is not included.

What the Extra Six Inches Buy You

Three situations where the 12in. runs out of reach:

• Deep tank: the taller the tank, the higher the arm has to climb for the light to cover the whole surface
• Sump or refugium: you're inside a closed cabinet with gear everywhere — the 18in. lets you route around whatever's in the way
• Clearance: when you want to work in the tank without banging into the fixture every time

The silicone coating protects the arm from moisture and cleans up easily when salt dries on it.

Specifications

• Max rim thickness: 1.20in. (30mm)
• Flexible arm length: 19in. (48.3cm)
• Total overall length: 22in. (55.9cm)
• Coating: silicone
• Cable management: 3 clips included
• Compatibility: AI Prime 16HD Reef, Prime 16HD Freshwater, Prime Fuge

Measure your rim before ordering. AquaIllumination doesn't publish a max thickness on its product pages — the figure above circulates among US retailers. If you're unsure, send us the measurement.

18 or 12 inch?

Take the 18in. if you need height or clearance. If your tank is a nano or mid-size and the light doesn't need to climb far, the 12in. (13in. arm, 16in. total) does the job and takes up less room.

One Installation Detail

The set screw in the base lets you twist the arm to sit the fixture flat. Tighten it hand tight only — no tools. And bend the arm before clamping it to the rim, never after: forcing an already-mounted arm puts strain on the glass for no reason. That counts double on the 18in., which works a longer lever.

What's in the Box

• 1 x 18in. Flex Arm
• 1 x Base screw
• 1 x Base plug
• 3 x Cable routing clips
• 1 x Allen wrench
• 1 x Base mounting gasket

Light not included.

Flex Arm, Tank Mount, or Hanging Kit?

• Flex Arm: the most adjustable. Bends by hand, works around obstacles.
• Tank Mount: the sturdiest and most precise. Two adjustable arms and a ball joint.
• Hanging Kit: the most discreet. Nothing on the tank, everything at the ceiling.

Why Choose ReefSolution

Authorized AquaIllumination dealer in Canada with technical support in French. Picking the mount is the most common mistake on the Prime line — send us your tank dimensions and rim thickness and we'll tell you which part to order. Shipping across Canada.

Complementary products:

• AI Prime Fuge 16HD — the refugium fixture: this is the most common pairing, since the 18in. is built to work over a sump
• AI Prime 16HD Reef Black — the nano reef fixture: 59W, 24 x 24in. coverage
• AI Prime Flex Arm 12in. — the short version: 13in. arm, 16in. total, for nano and mid-size tanks
• AI Prime Tank Mount Black — the rigid ball-joint mount, if you want it to never move

Frequently Asked Questions

Does the AI Prime Flex Arm 18in. work with the Prime Fuge?

Yes, and it's one of the most common pairings. The Prime Fuge, Prime 16HD Reef, and Prime 16HD Freshwater share the same 4.88 x 4.88in. housing. Over a sump in a crowded cabinet, the 18in.'s length and flexibility make all the difference. The Prime Flex Arm won't fit Hydra fixtures though — there's a separate Hydra Flex Arm.

Should you get the 18 or 12 inch Flex Arm?

The 18in. (19in. arm, 22in. total) is for when you need height: deep tank, refugium in a sump, or extra clearance above the water. The 12in. (13in. arm, 16in. total) covers most nano and mid-size tanks. If you're torn, send us your tank height.

What rim thickness does the Flex Arm handle?

Up to 1.20in. (30mm) according to the spec sheets circulating among retailers. AquaIllumination doesn't publish this figure officially, so measure your rim before ordering. Send us the measurement if you're unsure.

Does the arm hold its shape once bent?

Yes, that's the point of a gooseneck: it keeps whatever shape you give it. Bend it before clamping it to the rim, not after — especially with the 18in., which works a longer lever against the glass.