A recirculating aquaculture system (RAS) comprises a group of fish tanks that are connected as a single system and which includes filters, aeration and water pumps. These systems offer compelling advantages over alternative infrastructure options, especially in variable climates in temperate areas.
The fish in an RAS are fed and as they grow, they also utilise oxygen, which is replenished by means of aeration; the carbon dioxide that the fish release as a by-product is simultaneously removed by the same aeration. As the fish are fed they digest their feed and excrete solid and dissolved waste.
WATER MOVEMENT
Water moves continuously through the fish tank, carrying solid waste out of the tank and into the mechanical filter where it is trapped and accumulated for regular removal, usually daily, by staff when cleaning the filters. If left in the system, this waste will accumulate and compromise water quality.
The dissolved waste is comprised mainly of ammonia, which is converted to nitrate by the biological filter, in which desirable bacteria convert the highly toxic ammonia to benign nitrate, which can be allowed to accumulate within the system without negatively impacting the fish.
Daily water changes of around 10% of the system volume occur when the mechanical filters are cleaned. This is adequate to maintain the nitrate concentration at acceptable levels for fish health.
Diese Geschichte stammt aus der September 20, 2024-Ausgabe von Farmer's Weekly.
Starten Sie Ihre 7-tägige kostenlose Testversion von Magzter GOLD, um auf Tausende kuratierte Premium-Storys sowie über 8.000 Zeitschriften und Zeitungen zuzugreifen.
Bereits Abonnent ? Anmelden
Diese Geschichte stammt aus der September 20, 2024-Ausgabe von Farmer's Weekly.
Starten Sie Ihre 7-tägige kostenlose Testversion von Magzter GOLD, um auf Tausende kuratierte Premium-Storys sowie über 8.000 Zeitschriften und Zeitungen zuzugreifen.
Bereits Abonnent? Anmelden
Understanding eye conditions in horses: causes and first aid
A horse can get a swollen eye from bumping it against a tree, shaking its head to keep flies away, or even snake venom
IPM requires a completely different mindset
You need to investigate any beneficial insects that may appear on your plants, or you can purchase them
Does parrot farming protect wild species?
Those in favour of commercial captive breeding argue that breeding parrots to sell can relieve pressure on wild populations. Researchers Neil D'Cruze and Rowan Martin review the evidence.
Bacterial and fungal diseases of garlic
Garlic can be prone to bacterial and fungal diseases, and it's important that farmers are proactive in preventing infection and practise appropriate management. Magda du Toit reports.
Responsible wastewater management: a crucial part of farming
The inadequate management of waste water is a challenge that the agriculture sector needs to deal with. Magda du Toit spoke to experts in waste and water management about a cost-effective treatment system.
Technology that can help protect South Africa's farms
Farm attacks, murders, livestock and crop theft, and other rural crimes are a growing concern in South Africa. As a result, more and more farmers are turning to advanced security technology to protect their lives, properties, and livelihoods. Sinenhlanhla Mncwango spoke to experts about the security strategies that producers can adopt to combat these threats.
The impact of theft on farms in South Africa
A high number of livestock are being stolen every year in South Africa. Insurance is expensive and farmers are battling to find solutions to the problem, says Dr Lindie von Maltitz, agricultural economics lecturer in the Faculty of Natural and Agricultural Sciences at the University of the Free State.
Staying afloat amid the cost-price squeeze
John Hudson, head of agriculture at Nedbank Commercial Banking, spoke to Glenneis Kriel about the importance of environmental and social sustainability for a prosperous agriculture sector.
Free State has no reason to mark Transport Month
Free State Agriculture (FSA) is very concerned about the extremely poor state of rural paved and gravel roads in the province and has very little, if anything, to celebrate during Transport Month, which takes place every October.
SA's food system ‘vulnerable to climate change'
The Just Transition Agenda for Food System Policymaking in SA webinar, hosted by the Institute for Economic Justice (IEJ) in October, highlighted the role that South Africa’s food system plays in contributing to climate change and how vulnerable it is to the impact thereof.
