curing liverock

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curing liverock

Post  reefkeepersni on Wed May 25, 2011 7:13 pm

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 the transportation 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 extended periods and lack of light.

It is likely that many will even die. Additionally there are species that cannot even survive with in a 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 processed into relatively harmless compounds.

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

During this cycling period the ammonia level rapidly climbs as heterotrophic bacteria process the dead organisms. This high level of ammonia, with ammonia being toxic to most marine organisms, can have a synergistic effect and cause more organisms to die. Which will then in turn produce more ammonia. The populations of bacteria involved in the converting ammonia to nitrite 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 on and convert to nitrate. The nitrite to nitrate bacteria take a bit longer to build up a sufficient population 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 the nitrate 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 the system 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 or aquarium stores tanks. What this will allow is; greater control over the cycling period, the possibility of more organisms surviving this highly stressful period, and minimise the loss of mobile 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 the target aquarium or a large cycling tank, have a skimmer operating on the system, add large amounts of circulation and provide no lighting.

It is left there for about 2-4 weeks and the ammonia and nitrite levels are monitored.The circulation is required to allow good nutrient and waste exchange between the live rock and the water, to assist in the removal of any dying organisms from the rocks, and to minimise any areas that 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 algae blooms 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 to when the nitrite levels drop to undetectable levels.

Longer periods are possible, and in some rare cases the cycle seems to get stuck after the ammonia levels drop. The reason for this is still unclear, but may have something to do with inhibitors 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 the system via some mechanism.

The 'dark' technique of cycling of live rock is seen by the author as an out of date technique. It really should be avoided because there is no effort made to make the cycling period less stressful for 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 and low enough such that micro algae cannot bloom during this period of high nutrient levels, and remove as much of the waste from the system before it becomes converted into a pollutant or remove the pollutant from the system.

The best type of lighting to use is actinic as it is typically of the correct wattage and it supplies directly 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 using this 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 the system.

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 water changes 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 the time 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.

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