Without realising it, maybe most of us have been using recirculating aquaculture system (RAS) in our home aquariums for keeping our lovely ornamental fishes. So far, I rarely saw somebody using flow through system for their home aquarium. Did we study our aquarium system and how does it functioned to support the life of our aquarium fishes? If we did, perhaps it will be very easy for us to understand the RAS.
I believe everyone of us have some ideas about RAS, so I want to make the simplest explanation about RAS. The system work in a way where used water being moved into another cleaning system for cleansing purposes before being re-use back in the farming places. However, I used to see some system that do the cleaning process in situ, i.e. inside the farming tank itself. They move the water to some area of the farming tank and do the cleaning process before the water mixed back with the rest of farming water.
Why Go For RAS?
At least there are 5 reasons said in most of RAS textbooks on why people choose RAS for their fish (and aquatic organisms) farming system. Among the reasons is RAS can be operated in the unsuitable site for other type of farming. Since RAS normally a closed system, it will not depending so much on external factors. The internal environment perhaps can be "created" according to our species requirement. Second, it can be use in the area where water resources are poor, either in quantity or quality, either permanent or temporarily. RAS will not depending on external water resources to some extent. Third, it can be operated in the unsuitable climate for certain species. We can create our conducive internal climate in our RAS farm. Fourth, we can control or have more control over our production. Fifth, RAS can accommodate to environmental rules and regulations. However, for me, any other reasons such as logistic and market potential could also another reason why RAS was chosen. Personally, I choose the RAS because of the fourth factor, yes, I want to be in full control of my farm which I consider the most important aspect the fish farming management activities. I used to observe some other fish farming systems such as open water (sea, lake, lagoon and river) cages and ponds for groupers, seabass, threadfin, snappers, cobia and pompanos as well with molluscs and crustaceans. To my opinion, the open systems really can makes the management at the mercy of nature.
There will be few processes involved, mainly physical process in moving the used water into the cleaning place and physical, biological and chemical processes in the cleaning parts. We will see what are the processes involved in an recirculating aquaculture system (RAS) later (not including the biochemical processes that going to take place inside the body of our cultured organisms).
Function Of Water In RAS
As in the name of the system, it will recirculate at least the water in the system (depending on how good the cleaning process of the system take place, otherwise, it will also recirculate some unnecessary element). Since we are keeping our groupers in the enclosed tanks, we must not only look at the water recirculating process similar to air conditioning process in the a crowded places, but it work almost like the oxygen supply in the hospital intensive care unit. Our fishes will need the water as their living media and as their life support system. The recirculated water should bring along both basic functions, conditioning and life supporting. However, that 's not all the functions of the water in RAS. It will functioned as cleaning media for the system just equally to the same function of the blood in our body. So, the recirculating of water will cover at least few processes: refreshing of living media, bringing in oxygen and cleaning the system.
The recirculating process in RAS normally done with the use of pumping system. We should discuss about the pumping system in RAS sometime later.
The Removing Of Unwanted Materials
When keeping our groupers in the tanks, they depends solely on the feeds given to them for their growth. We could be fully aware that every time we feed the fishes, there are some amount of the feeds were not eaten by the fishes. It will drop to the bottom of the tank, broken into pieces or swelled due to water absorption and some becoming the suspended solids in the water. At the same time, the fishes will excrete their metabolites through their feces. These will become our first problems, removing solid waste and suspended solid waste .After sometimes, the excess feed and faeces will disintegrated becoming smaller particles and require to be removed with other dissolved organic materials.
The breaking up of the uneaten feed will involve few physical and biochemical reactions or processes.The process of breaking up of feed and feces will require oxygen and this will creating demand for oxygen inside our system. Remember, our grouper fishes also require oxygen for their life and they also excrete carbon dioxide from their respiration process.
The eaten feed will be used by our fishes for growth and getting energy. In order to gain the energy, the feed components will be oxidized which will require oxygen and excrete carbon dioxide. Ammonia is another waste product of the breakdown of the protein in the feed. So, our fishes will consume foods and use oxygen for breathing and oxidation of the feed. The farming water will be the polluted with the uneaten feed, faeces, excretion of carbon dioxide and ammonia.
In the next posting, I will try to elaborate how cleaning processes being done in RASRAS or order from our supplier. Do not build or buy without knowing our real requirement of every components in RAS. We may end up building excessive or undersized components of our RAS. Since RAS is a life support system and life keeping system, anything below standard requirement will be hazardous to our grouper fishes while excessive mean more money needed for our initial investment, something that any investor will try to avoid.
I believe everyone of us have some ideas about RAS, so I want to make the simplest explanation about RAS. The system work in a way where used water being moved into another cleaning system for cleansing purposes before being re-use back in the farming places. However, I used to see some system that do the cleaning process in situ, i.e. inside the farming tank itself. They move the water to some area of the farming tank and do the cleaning process before the water mixed back with the rest of farming water.
Why Go For RAS?
At least there are 5 reasons said in most of RAS textbooks on why people choose RAS for their fish (and aquatic organisms) farming system. Among the reasons is RAS can be operated in the unsuitable site for other type of farming. Since RAS normally a closed system, it will not depending so much on external factors. The internal environment perhaps can be "created" according to our species requirement. Second, it can be use in the area where water resources are poor, either in quantity or quality, either permanent or temporarily. RAS will not depending on external water resources to some extent. Third, it can be operated in the unsuitable climate for certain species. We can create our conducive internal climate in our RAS farm. Fourth, we can control or have more control over our production. Fifth, RAS can accommodate to environmental rules and regulations. However, for me, any other reasons such as logistic and market potential could also another reason why RAS was chosen. Personally, I choose the RAS because of the fourth factor, yes, I want to be in full control of my farm which I consider the most important aspect the fish farming management activities. I used to observe some other fish farming systems such as open water (sea, lake, lagoon and river) cages and ponds for groupers, seabass, threadfin, snappers, cobia and pompanos as well with molluscs and crustaceans. To my opinion, the open systems really can makes the management at the mercy of nature.
There will be few processes involved, mainly physical process in moving the used water into the cleaning place and physical, biological and chemical processes in the cleaning parts. We will see what are the processes involved in an recirculating aquaculture system (RAS) later (not including the biochemical processes that going to take place inside the body of our cultured organisms).
Function Of Water In RAS
As in the name of the system, it will recirculate at least the water in the system (depending on how good the cleaning process of the system take place, otherwise, it will also recirculate some unnecessary element). Since we are keeping our groupers in the enclosed tanks, we must not only look at the water recirculating process similar to air conditioning process in the a crowded places, but it work almost like the oxygen supply in the hospital intensive care unit. Our fishes will need the water as their living media and as their life support system. The recirculated water should bring along both basic functions, conditioning and life supporting. However, that 's not all the functions of the water in RAS. It will functioned as cleaning media for the system just equally to the same function of the blood in our body. So, the recirculating of water will cover at least few processes: refreshing of living media, bringing in oxygen and cleaning the system.
The recirculating process in RAS normally done with the use of pumping system. We should discuss about the pumping system in RAS sometime later.
The Removing Of Unwanted Materials
When keeping our groupers in the tanks, they depends solely on the feeds given to them for their growth. We could be fully aware that every time we feed the fishes, there are some amount of the feeds were not eaten by the fishes. It will drop to the bottom of the tank, broken into pieces or swelled due to water absorption and some becoming the suspended solids in the water. At the same time, the fishes will excrete their metabolites through their feces. These will become our first problems, removing solid waste and suspended solid waste .After sometimes, the excess feed and faeces will disintegrated becoming smaller particles and require to be removed with other dissolved organic materials.The breaking up of the uneaten feed will involve few physical and biochemical reactions or processes.The process of breaking up of feed and feces will require oxygen and this will creating demand for oxygen inside our system. Remember, our grouper fishes also require oxygen for their life and they also excrete carbon dioxide from their respiration process.
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| The impact of the fishes on the farming water. Photo: Mahmud Ismail. |
In the next posting, I will try to elaborate how cleaning processes being done in RASRAS or order from our supplier. Do not build or buy without knowing our real requirement of every components in RAS. We may end up building excessive or undersized components of our RAS. Since RAS is a life support system and life keeping system, anything below standard requirement will be hazardous to our grouper fishes while excessive mean more money needed for our initial investment, something that any investor will try to avoid.
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