Live rock, aquascaping and cycling a new setup
by Clive

Live rock (‘LR’) is remnants of coral reefs which are ‘farmed’ in tropical countries (commonly Fiji and Indonesia) and have usually been colonised by small life like tube worms, tunicates, algae, and most importantly for reefkeepers, the bacteria which break down ammonia, nitrites and nitrates.
In most modern systems, live rock is the only form of biological filtration (the so-called 'Berlin method’). Its advantage over other methods (trickle filters, canister filters, etc.) is that it will remove nitrates instead of allowing them to build up. As it is the heart of a reef tank, it is worth buying the best rock you can afford.

Other types of rock
Tonga branch rock can add variety to your aquascaping, but is usually more expensive than normal LR:

Reef bones. These are dead live rock! That is, coral remnants that are not colonised by bacteria or other life. They can be mixed with LR to save money, and will eventually become colonised by beneficial bacteria, though cycling will take longer.
Ocean rock is just normal rock (e.g. limestone). It is heavy, dense and unsuitable as a biological filter as it isn't porous enough.
Tufa rock (the staple of many marine systems until recently) is similarly unsuitable for filtration and can also absorb phosphates and other substances, which can later leach into the tank.

Live rock can be obtained ‘cured’ or ‘uncured’. Cured rock is ready to be put into the tank immediately, whereas uncured rock needs treating before use: a separate tank or large water container must be set up with salt water, a heater and a powerhead for flow (the garage is a good place for this, as uncured rock can smell revolting!). The whole curing process will take some time: several weeks may be necessary until ammonia and nitrite levels are as near zero as possible.

Buying live rock

It can be bought from most local fish shops, online or from fellow reefers who are breaking down their systems. Most people recommend 1 kg of LR for every 2 gallons of water, but the most important factor is that the rock should have plenty of flow around and through it (see below).

Buying from a LFS has the advantage that the LR can be inspected and selected for size and shape. Try to find pieces which are porous and light for their size, with plenty of caves and holes. Avoid any rock which is kept with livestock, as you don’t know what diseases may be carried on it, or whether the shop has used copper as a treatment. LFS rock may be quite expensive unless you are lucky enough to live near one that specialises in it.

Buying online may have the benefit of lower prices, but obviously the LR can’t be inspected. Many UR sponsors sell good quality rock relatively cheaply, and delivery is often included and next day by courier.

Buying from fellow reefers can be the cheapest way of acquiring rock, and has the advantage that the LR is cured and has its full complement of beneficial bacteria. Find out how long the rock has been in the tank; avoid pieces over 5 years old as coralline, algae, etc may have reduced the rock’s porosity, making it less effective. There is also a risk of introducing harmful or nuisance critters (aiptasia or majano anemones, for example) or disease organisms, so try to find out if the owner’s tank has suffered from any disease outbreaks.

Preparing the tank

As already mentioned, the flow around and through each piece of LR must be maximised to allow it to work efficiently as your biological filter. Many reefkeepers use a ‘reef rack’ made of ‘egg crate’ (a hard plastic grid as used as ceiling light diffusers) to stand the rock on. This has the advantage of allowing flow under the rock and avoiding the build-up of detritus. A powerhead or the outflow from a closed loop can be used to direct flow under the rack. The egg crate can be cut to shape and is raised from the tank bottom, usually by making legs of hard piping:

The 'legs' can be vertical or horizontal and can be attached using plastic zip ties. Holes can be drilled in them to avoid dead spots with no flow. Some reefkeepers find that the rack is difficult to hide from view and decide not to use one, but an arrangement of smaller rock pieces in front of the crate can serve to camouflage it.

The tank should be filled and the desired specific gravity and temperature reached before the LR is introduced.

When your LR arrives

It is important to introduce cured LR into the tank as soon as possible to prevent all the life on it from dying off. If you are short of time, put it in immediately and do the aquascaping later. Inspect each piece before locating it. It should be obvious which way up it has been, with coralline and other algae at the top. Make sure it's the same way up in the tank, as this will minimise die-off.

Aquascaping is very much a matter of taste, with some people having a ‘wall of rock’ effect and others preferring one or more towers of rock with swimming space around them (have a look through ‘Members’ tank specs’ for ideas). Again, the priority is for plenty of flow, so try to ensure that your aquascaping does not leave dead spots with little or no water movement. Try to make plenty of caves and tunnels, both to maintain flow through the rock and provide shelter for shy or cave-loving livestock. Make sure that the rock is stacked with the largest pieces at the bottom and arranged so that it can’t slip or fall (you don’t want cracked glass or flat livestock!). Many people use zip ties (having drilled holes in the rock), acrylic dowel and / or reef putty (e.g. ‘Milliput’) to fix pieces together and ensure stability.
If a reef rack is not used, put the base pieces on the tank bottom and any sand around it – some livestock can burrow under rock and destabilise it.


Although the LR is cured, it will not have its full quota of bacteria yet, so the tank must not be stocked immediately. No matter how much care is taken, there will normally be a certain amount of die-off, which will provide nutrients for beneficial bacteria to multiply. Test the water daily: ideally pH should be 8.0 – 8.3 (expect this to fluctuate at first) and specific gravity 1.024 – 1.026. There will normally be an ammonia ‘spike’ at first, followed by an increase in nitrite. As these then start to dwindle, nitrate will start to rise. When this begins to fall again, the first of the clean-up crew can be introduced. Cycling may take 28 days or less, depending on the quality of the LR and how much die-off there has been.

Run the tank from day one as you would when it's stocked. Use phosphate remover immediately: phos can be absorbed by rock and give you trouble as it's leached back into the water. You can also run carbon (use a good one like Rowacarbon, as cheap ones can contain silicates and phosphates). All this will accustom life to your tank conditions.


Some reefkeepers use full lighting from day 1 to ensure that photosynthetic life suffers the minimum die-off. An alternative is to introduce the lighting regime gradually to minimise algal growth until the clean-up crew is ready to go in.
You can use this schedule:
- days 1-4 no lights
- day 5 actinics for 2 hrs
- day 6 actinics 4 hrs
- day 7 actinics 6 hrs, main lights for 2 hrs (concurrently)
- day 8 actinics 8 hrs, mains for 4hrs

and so on, until you get to your preferred lighting regime.

Some will recommend using bacteria solutions (unnecessary as the LR is already colonised) or ‘feeding’ the tank with a prawn, etc. You don't need to feed at all during cycling - the tank will have only a limited ability to process waste.

Watch what develops (my favourite part!). Invest in a magnifying glass - it's fascinating. Try to get rid of any nasties asap, as it can be very difficult once the tank is stocked.

Be as patient as you possibly can with stocking - both fish and inverts, to give your LR time to adjust to the new nutrient load.