Life Rock Arch XL 24"

• 61 cm single span - one uninterrupted arch rather than a stack of small pieces, so there are no visible joins and nothing to bond together.
• About 11.3 kg in one piece - heavy enough to sit on the base glass under its own weight without putty in most scapes.
• 25 to 30 cm wide at the widest point - the arch has genuine depth front to back, so it reads as a structure rather than a cut-out.
• Aragonitic base rock, not cement - real aragonite with around 50% void space running through it, which is where nitrifying bacteria colonise.
• Spored bacteria infused - CaribSea's AragAlive treatment, which shortens the cycle without removing the need for one.
• No curing and no die-off - dry rock carries no collected marine life, so there is no ammonia spike from the rock and no weeks spent curing in a bin.
• Hand-made and one-off - CaribSea states dimensions and weights vary between pieces, so the arch you receive is not the one in the photograph.

The XL is a centrepiece, and the deciding number is length. Our rule for a feature rock is that it should span no more than about half the tank's length, so water still moves freely around and behind it.

Then check depth. The arch is 25 to 30 cm front to back at its widest, so a tank with less than about 45 cm of front-to-back depth will have it pressed against the back glass with no room to clean behind. Height matters too: allow enough water above the arch that fish are not swimming through the top few centimetres of the tank.

• One Life Rock XL Arch, 24 inches (61 cm) long
• Approximately 25 lb (11.3 kg) of rock

Not included: base rock, sand, reef putty or cement, and any bacterial starter. Because each arch is hand-shaped, both weight and profile vary from piece to piece.

An arch is the feature; base rock is the bulk. The widely used guideline, and the figure CaribSea's own Life Rock listings quote, is 1 lb of rock per US gallon of display volume - about 0.12 kg per litre. The table shows what the XL Arch contributes and what is left to make up.

Plenty of modern reef scapes deliberately run below these figures to keep open sand and cleaner flow. Read the table as the traditional upper bound rather than a shopping target.

CaribSea notes that these are hand-made products, so dimensions and weight vary between pieces. The figures above are typical, not guaranteed.

A single heavy arch behaves differently to a stack of small rocks, and it is worth planning before it is wet.

Seat it on the base glass, not on the sand. Sand settles and burrowing fish undermine anything resting on it, and an 11 kg piece that shifts against a glass panel is a real risk rather than a theoretical one. Add sand around the arch afterwards.

Check the arch sits on at least three contact points before you fill. If it rocks, shim it with a flat offcut of base rock rather than relying on the sand to hold it level.

On a bare-bottom or acrylic tank, a foam or eggcrate pad under the contact points spreads the load and stops point pressure on the base.

Life Rock is dry rock with bacteria added, not ocean-collected live rock. There is no die-off, which is why CaribSea can say no curing is required. What the spored bacteria do is give the biological filter a head start.

They do not replace the cycle. A new tank still has to grow a bacterial population sized to its stocking level, so dose ammonia or add livestock slowly and test until ammonia and nitrite both sit at zero.

Suitable for: marine and reef aquariums from about 120 cm; fish-only setups where a single dramatic swim-through matters more than lots of caves; aquascapes being built from scratch; and hard alkaline freshwater tanks such as Malawi and Tanganyika displays.

Not suitable for: tanks under about 90 cm, where a 61 cm arch dominates and kills flow; planted, blackwater, shrimp and discus systems, because calcium carbonate raises pH and hardness; and anyone specifically wanting the biodiversity of collected live rock. It is also not a shortcut past cycling a new system.

The rock needs no scheduled maintenance. In a marine tank the manufactured coating is gradually overgrown by real coralline algae, usually within the first year, after which the piece stops looking new.

Blow detritus out from under the arch at water changes with a turkey baster or a powerhead. A large single span shelters more dead water than open rock does, and trapped detritus is what feeds nuisance algae.

Chips in the coating from handling are cosmetic. The aragonite beneath colours in on its own once coralline establishes.

• CaribSea South Seas Base Rock 18kg - the plain bulk rock that makes up the balance shown in the table above.
• CaribSea Life Rock Shelf Rock 18kg - flat plates for coral shelves either side of the arch, in the same finish.
• CaribSea Arag-Alive Fiji Pink - live aragonite sand to dress the base once the arch is seated.
• CaribSea Purple-Up - calcium and strontium supplement aimed at bringing coralline algae over the coating faster.
• Life Rock Arch 12" 4pk - four smaller arches, if your tank is under 120 cm or you would rather build a series of tunnels.

CaribSea does not publish a warranty term for Life Rock. Your rights under the Australian Consumer Law apply regardless and are not limited by anything the manufacturer does or does not offer.

This is an oversize, fragile item. The Australian distributor notes that because of the fragile nature of this rock, pieces can break in transit, and a 61 cm single span is the most vulnerable shape in the range. Unpack and inspect on arrival. A broken arch is still sound rock and usually makes two good overhangs, but if you need the span intact, check the box before it is signed off.

How big is the CaribSea Life Rock XL Arch?

It is 24 inches (61 cm) long, roughly 25 to 30 cm across at its widest point, and weighs around 25 lb (11.3 kg). Each arch is hand-made, so CaribSea states dimensions and weight vary between pieces.

What size tank does it suit?

A 120 cm tank is the natural fit, where the arch spans about half the length and leaves room for flow at either end. It works in 150 cm and 180 cm tanks too. In a 90 cm tank it takes up 68% of the length and crowds the scape.

Does it need curing before it goes in?

No. CaribSea states no curing is required. It is dry rock with no collected marine life on it, so nothing dies off and the rock itself releases no ammonia. The aquarium still needs to be cycled before stocking.

Do I need reef putty to hold it in place?

Usually not. At around 11 kg the arch is heavy enough to sit stably on the base glass on its own, provided it makes at least three solid contact points and does not rock. Use putty if you are stacking anything on top of it or if the piece will not sit level.

Will it look the same as the photograph?

No. Every arch is individually shaped, so profile, colour distribution and exact weight differ from piece to piece. The photograph is representative of the shape and finish rather than of the specific rock you will receive.

Is one XL Arch enough rock for my tank?

On its own, no, for most tanks. At 11 kg it covers the traditional rock requirement of a 90 litre tank. In a 200 litre or larger reef it is the feature piece and you will want base rock alongside it - see the table above for the balance.