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Cycling Live Rock

By Dallas Warren. Presented 08/10/1997 on #reefs IRC.

What Is Cycling Of Live Rock?

Typically after live rock is collected from a reef rubble area, it has to be transported to a dealer,an aquarium store, and then finally to the aquarists.. The problem is that during each of thetransportation or storage periods less than ideal conditions are provided for the live rock.

Many of the organisms become unduly stressed by stewing in their own wastes for extendedperiods and lack of light.

It is likely that many will even die. Additionally there are species that cannot even survive withina reef aquarium for various reasons. Cycling allows the dying animals and plants contained onthe rock to die off and the resulting products from the decay of the tissue to be further processedinto relatively harmless compounds.

The cycling period gives an aquarist an opportunity to see evidence of the ammonia cycle, ornitrification which is the conversion of ammonia to nitrate.

During this cycling period the ammonia level rapidly climbs as heterotrophic bacteria process thedead organisms. This high level of ammonia, with ammonia being toxic to most marineorganisms, can have a synergistic effect and cause more organisms to die. Which will then inturn produce more ammonia. The populations of bacteria involved in the converting ammonia tonitrite quickly build up to sufficient numbers to process the waste generated and the ammonia levels go down to undetectable levels (by aquarist test kits).

Nitrite then becomes the dominant toxic species present, which another group of bacteria feed onand convert to nitrate. The nitrite to nitrate bacteria take a bit longer to build up a sufficientpopulation to handle the waste, but then the nitrite levels will become undetectable by aquarist test kits. This is the important part at this point but later denitrification can start and remove thenitrate which starts to increase in concentration.

It is possible to buy live rock cycled, partially cycled or almost straight from the reef. If the liverock is going to be utilised in an existing reef aquarium then cycled live rock should be used.This will minimise the peak in ammonia and nitrite caused by the addition of the rock to thesystem as there will be very little die off. In a well maintained tank it is even possible to add some additional live rock to the system without any visible adverse effect to the inhabitants.

It is preferable to cycle the live rock in the target aquarium, not in the collectors, dealers oraquarium stores tanks. What this will allow is; greater control over the cycling period, thepossibility of more organisms surviving this highly stressful period, and minimise the loss ofmobile organisms that can leave the rock.

How this can be done is discussed in the following section.

How Do You Cycle Live Rock?

The current general procedure for cycling live rock is to throw it into a large container, either thetarget aquarium or a large cycling tank, have a skimmer operating on the system, add largeamounts of circulation and provide no lighting.

It is left there for about 2-4 weeks and the ammonia and nitrite levels are monitored.Thecirculation is required to allow good nutrient and waste exchange between the live rock and thewater, to assist in the removal of any dying organisms from the rocks, and to minimise any areasthat may go anaerobic.

Areas may become anaerobic because of a large organism dying and the large oxygen usage bythe bacteria processing the tissue. No lighting is provided to avoid any excessive micro algaeblooms in the system while nutrients are at an elevated level.

The length of the cycle takes around 2-4 weeks, from the time the rock is placed in the vessel towhen the nitrite levels drop to undetectable levels.

Longer periods are possible, and in some rare cases the cycle seems to get stuck after theammonia levels drop. The reason for this is still unclear, but may have something to do withinhibitors for the nitrite to nitrate bacteria (which are more sensitive to environmental conditions and slower growing than the ammonia to nitrite bacteria) being introduced into thesystem via some mechanism.

The 'dark' technique of cycling of live rock is seen by the author as an out of date technique. Itreally should be avoided because there is no effort made to make the cycling period less stressfulfor any of the organisms present.

There is a much better way to do it which will provide a higher survival rate.

The idea is to; provide enough light to photosynthetic organisms such that they can survive andlow enough such that micro algae cannot bloom during this period of high nutrient levels, andremove as much of the waste from the system before it becomes converted into a pollutant orremove the pollutant from the system.

The best type of lighting to use is actinic as it is typically of the correct wattage and it suppliesdirectly the wavelength ranges that the photosynthetic organisms utilise. So far as a rule of thumb around 0.14 W/lt (1 W/gal) is a sufficient level to use.

The lights are operated on an increasing length of time during the cycling period, starting at around 6 hours per day, then increasing an hour every couple of days until the full day length is reached. Note that this is based on the authors own experience and that of another aquarists usingthis technique that the author has communicated with.

Further experimentation in this area could be done to further clarify this, but in the cases where it has been use there has been a good survival. Once the cycling is over, then the other lighting can then be gradually phased in. Need to avoid any sudden addition of light as this will stress any photosynthetic organism as they take time to adjust to new lighting levels.

In addition to the lighting used, continuous operation of a skimmer, activated carbon, and regular water changes should be implemented. These activities are used with the idea of transporting as much of the waste and pollutants from the water, therefore reducing stress in thesystem.

The use of the skimmer and activated carbon removes compounds before they can be broken down by the heterotrophic bacteria. Water changes remove compounds before they can breakdown, but also remove some of the toxic ammonia, nitrite and other pollutants from the system.

There is no reason to worry about substantially prolonging the cycling period by using waterchanges because the amount of nutrients for the bacteria has been reduced. This is a myth.

Bacteria will grow and multiply at a exponential rate, with all environmental factors staying constant, until there is a high enough population to process all of the available nutrients. At this point the population will stablise.

A change in the nutrient level, which will change the end population required, will make a very small change in the time frame required to reach this point because of the exponential growth rate. Additionally at the end of the cycling period, all of the dead organisms have been processed so there is now a reduced amount of nutrients available.

The bacteria population will adjust to the level to process the amount of nutrients now being generated in the system by living organisms. This will most likely result in a reduction in the population from a peak during the cycling period. There is no way that initially an operating system will generate as much nutrients as is generated during the cycling period. Therefore reducing the amount of waste and nutrients will not influence the final bacteria population or thetime frame to any large extent.

The recommend method of cycling live rock is summarised as follows:

  • As the live rock is unpacked remove any white, slimy areas and anything else that is decaying. The white spots where an organism, typically a soft coral, hard coral or sponge, has died. Removal will help to minimise the stress on the system by removing another source of nutrients.
  • Clean off some of the invertebrates on the rock, such as sponges and corals. But unless you know what you are removing and are experienced they you may remove some very valuable specimens. There is no need to be so harsh and take to it with a brush and scrub it clean. This practice is rather excessive.
  • Inspect each rock for the presence of bristle worms and remove any if found. Bristle worms have a tendency to come out of the rock, or hang partially out, after the rock has been in transit.
  • It is a good idea to remove any plant growth, both macro and micro algae, as these can easilyre-grow from the root system left behind.
  • Arrange the live rock in the aquarium. Ensure that only small areas are in contact with the bottom of the aquarium and between the rocks. This will ensure good water circulation around the reef structure. Working towards small contact areas between the rocks also helps to build an open reef structure with many tunnels, arches, overhangs and caves. This has the added bonus of making a much more interesting reef structure to look at.
  • Position return and circulation pump outlets such that there is good water movement throughout the entire reef structure. In dead spots detritus will accumulate. This can be use to an advantage by making a spot where detritus can settle that is easy to access. Then regularly the detritus can be siphoned out of the system.
  • A mechanical filter can be used during this period to help remove suspended solids from the system, but ensure that it is cleaned regularly, every day is preferred. This is because the material the filter catches is not removed from the system. It will continue to break down and contribute to the addition of pollutants in the system.
  • Operate the skimmer continuously and tune such that a dry, dark foam is collected.
  • Keep activated carbon in a high flow area of the system such that the water passes through it.Once the cycle is over use activated carbon as usual, whether intermittently or continuous.
  • Operate the actinic lighting from the beginning, starting with about a 6 hour photo-period.Gradually increase this by an hour every couple of days until the full day length of 12-14 hours is attained.
  • If white spots appear on the rock or something appears to be dying then siphon or remove it from the rock.
  • Regularly perform partial water changes and siphon out any detritus that has settled anywhere in the system.
  • The more frequent these water changes the better, as this helps to keep the levels more constant without giving huge swings. The amount of the water change can vary, but a 50% is a good start. If there are problems with such a high volume change then decrease to a level that is possible. But the higher the water change the better as it will remove more of the nutrients and pollutants.
  • When the cycling period is over, with ammonia and nitrite levels undetectable, start to phase in the main system lights. Do this gradually to reduce stress on the photosynthetic organisms present and to avoid a micro algae bloom.
  • Start a regular maintenance program, including water changes at the length and volume for a normal operating system. This varies, but around 5-10% of the system volume per month is currently recommend. But higher and lower levels have been successfully used by various aquarists.

Ok, that is it people, time for some questions..

<starfish> Q - In an effort to reduce the die off and maintain as many original organisms as possible, can commercial bacteria products?

<DBW> Commercial bacteria products can be used, and I know many people actually swear bythem....

<DBW> but I think that these are a waste of money...

<DBW> with the rock that you add to the system there will be many different species of bacteria present....

<DBW> and these just have to have time to multiply...

<DBW> additionally adding just some bacteria to the tank from a bottle, these bacteria will go into shock, as the condtions are so much different to that in the tank....

<DBW> it will take them some time to adjust and start to grow...

<DBW> and within this same time the natural bacteria will have mutliplied anyway DBW

<starfish> Have you heard of the TLC bacteria in a bottle? And is it any good?

<DBW> I am not too good on brands, I am in Australia, and we are rather limited to the range of products that we can get, sorry DBW

<starfish> How can I cure rock, if it has SPS corals on it?

<DBW> Just use the same technique, but with the fact that them is a more nutrient .....

<DBW> poor likeling coral on there, you should be more thorough with the procedure...

<DBW> make sure you keep the nutrient levels as low as possible, and provide some light for it to ...

<DBW> photosynthesis just at a bare minimum to keep it alive DBW

<starfish> Q: Some live rock dealers recommend rinsing new live rock in fresh water. Is this a good idea? What about rinsing in salt water?

<DBW> That may be a good idea, rinsing in freshwater may help to kill any smaller types of organisms...

<DBW> ones that will not be able to handle the large concentration diff across the cell membranes when they are immersed...

<DBW> will also help to remove any detritus that is already on the rock....

<DBW> as for SW, the only good point that will have is to rinse of any detritus DBW

<starfish> What is the best live rock? Florida, Fiji, etc..

<DBW> This is from only what I have heard from other aquarists in the USA, here we can only get that straight from the GBR, .....

<DBW> that from the Pacific is ment to be lighter, lower density than Gulf rock.....

<DBW> and that from Tonga is very branched and beyond that I cannot recall....

<DBW> but I do know that we can get good stuff off the GBR.. but you guys can't get that ;-)DBW

<starfish> What is the best way to remove mantis shrimp? I have tied the FW baths but they seem harsh.

<DBW> There are traps available, and these work well...

<DBW> but the best way to do it is if you know which rock they are in...

<DBW> in this case you pull out the rock, then pour soda water into the hole....

<DBW> and you will have animals flying out of the rock left right and center....

<DBW> Do this over a container so that you can catch anything that comes out

<DBW> Other than that, they are very hard animals to catch, they are very intelligent DBW

<starfish> Why do we want to kill small organisms? I thought the whole point of your improved procedure was to keep more of them alive.

<DBW> OK, that Q caught me there a bit, just give us a sec......

<DBW> Now you do not want to kill off any small organisms, .....

<DBW> the only ones that you could benefit from to kill off is ones that cause disease, such as Ick....

<DBW> these guys are very sensative to the osmotic pressures....

<DBW> a fresh water dip will cause them damage. Personally I would not do a freshwater dip with my live rock, but there are many techniques out there, so you just have to decide for yourself which you prefer to use


<starfish> Q - What is LR from the GBR like?

<DBW> I don't have much to compare it too, except pics online, but from what I can see there is a good mix of...

<DBW> coralline algae, purple, pink, red, green...

<DBW> there are also a lot a inverts come along for the ride....

<DBW> my tank has extensive zoanthid colonies that came with the rock.. .

<DBW> The shape is highly variable and it depends on the collector there....

<DBW> if you are lucky then you can end up with some really nice long and narrow piecesDBW

<starfish> Should you use anyt additves in the live rock holding tank while it is cycling?

<DBW> That I suppose is refering to calcium, iodide, buffers etc.....

<DBW> You want to maintain as close as possible to normal system values. And this can be very difficult considering what is occuring.....

<DBW> in the tank. On top of this you may be changing water continuously......

<DBW> you can keep track of the levels in the tank, and if they get too far out of the range they should be in then ...

<DBW> if would be an idea to use them, especially the buffers, as this will help maintain the pH levels...

<DBW> calcium is not quite as important, as long as the levels stay high, and they should as it should not be being used up and there is continual water changes that will help to keep the levels up DBW

<starfish> What's your philosophy on the type of LR to use in constructing a Reef structure in our tanks--Tonga + W. Pac. + ?

<DBW> What you are after in the end product it a reef...

<DBW> that is open to allow good water circulation and spots to place corals and any other organisms you wish to maintain in the tank

<DBW> The Tonga rock is good because of its highly branched nature....

<DBW> this is perfect for making great arches through the reef.....

<DBW> But I think a tank made exclusively with this looks a bit funny, I like to have somemore 'bulky' type of rocks...

<DBW> so at the end of that, just add some Tonga to make a more interesting structure, but this can be achieved using with W Pac rock anyway.


<starfish> Is there a way to visually distinguish between Pacific and Caribeean live rock?

<DBW> Hmmmmmm......

<DBW> That would be difficult, and is a bit out of my league there as I have not had a chance tohave a close look at both types....

<DBW> but as a rough rule, the Carribean is more dense in structure, will be very heavy for its size....

<DBW> and that from the Pacific less dense, lot lighter and will look porous....

<DBW> That is the best I can do DBW

<DBW> Well that is it, hope that helped a few of you along.

Created by liquid
Last modified 2006-11-26 06:03