Following is some practical advice if you are planning on venturing into the world of home aquaculture, or farming fish for food in your backyard. In this article we provide you with an overview, what to grow, specific requirements for the different varieties of fish and how to prepare them for the plate.
Did you know that the most kept and popular pet in the world is the Goldfish? Fishing as a pastime is hugely popular, whether at sea, off a boat, jetty or river. In fact I doubt you will find very few people that have never fished or kept fish at some stage in their lives. So it really isn’t any wonder that people now have a very strong interest in home aquaculture, literally growing fish for food in their backyard.
Firstly, my personal experience in keeping fish started 10 years ago, with my knowledge being gained from my the families combined 30years of fish keeping using natural methods, hands on experience, and that of the 1,000’s of customers, hobbyist and commercial breeders we speak with and learn from.
There are loads of variables, methods and information available on the topic of aquaponics, growing edible fish and home, I am hoping that the following list will help you have a better understanding when you start your own research.
You will need a pond to hold the water, a pump to move the water, and a filter to clean the water. The size of the pump and the filters, (be it, biological, plant filter or aquaponics grow bed) will be directly related to the size of pond you select and the amount of fish you wish to grow at any one time.
Whatever body of water you have, you will need a pump that will push this amount of water through a filtration system 24 hrs a day.
All filtration methods take time to accumulate beneficial bacteria, generally 3-4 months, you can’t rush this process, so don’t overload it with too many fish too soon, start with a small number and then increase gradually over the next month or so.
Excluding bore water, concrete or earthen based ponds, PH levels will rise and fall over the course of the day and night, sunlight, fish, plants, fish food etc. all have a bearing on the PH levels. Checking and trying to adjust the PH artificially is almost impossible.
If you are unsure about this suggestion, take a PH reading in the morning before the sun hits to water, for 5 consecutive days and calculate the average reading, this is your baseline PH for your system. If the reading is in the normal range you can confidently stop testing and worrying. In the end you want to be growing fish that are suited to the environment you can offer, rather than fighting it all the time.
Ammonia, Nitrates and Nitrites
Ammonia, Nitrates and Nitrites are all part of the natural chain of events going on in you pond every hour of every day when fish are present. A mature, correctly sized and maintained filtration system will cope with these elements and keep the water healthy.
All filtration systems, particularly aquaponics grow beds will benefit from using Zeolite, (the naturally occurring volcanic rock that absorbs ammonia). For best results you can disperse this into you growing medium of your aquaponics, (10kg per 2square meters or grow bed) there it will absorb any ammonia and excess nutrients that the plants don’t take up, this is then stored within the grow bed. Zeolite will only release the held ammonia when the root system of the plant asks for it, effectively bridging the gaps between what your fish produce and what your plants take up.
All fish require oxygen, as air passes across the water, oxygen is infused, pumps that create splashing or spraying will assist with this process, running an air pump with air stones is not critical, but it is definitely helpful, especially if you are using a flood and drain method or if your pond is sheltered, covered, indoors or heavily stocked.
To maximize growth, feed small amounts regularly, from once a day, up to 5 times a day is acceptable.
The most important thing is to ensure there is no excess food left uneaten, if there is, scoop it out. Happy fish feed, if they are not coming up for food, they are not happy, and this is the best indicator about the health of your fish.
Moving Fish from one location to another is one of the most stressful events in the life of a fish, you can minimize this with careful handling, but you can never really eliminate the risk of death. If the fish are not coping they will start to show signs of stress generally within the next 2 weeks, so keep a close eye on them be ready to respond.
In most cases of a fish tolerate well, moving locations, introduction of new fish or plants, cleaning out the pond or the filter, but any of these events can result in unhappy, sick fish. Signs of ill health are not eating, isolating themselves, hanging on the bottom or the top of the pond, white film on the skin, tail or fins, if this is present in just one fish, you can afford to be patient and let nature take its course, if the bulk of the population is acting this way you need to act quickly.
Use of medicating chemicals with fish you plan to eat, is not advisable, so to help the fish, to do an immediate 1/3 water change (make sure you condition the water if it is from a tap), add 3kg of pool salt to every 1,000lt of water, (i.e. 500lt use 1.5kg), ensure that there is plenty of moving water and or use an aerator. Reduce feeding to an absolute minimum. The fish should remain in salt until they are looking sociable and interested in food, you can test this by throwing tiny amounts of pellets in. When you think they are looking better do 1/3 water changes over the next week or two to bring the water back to fresh, remember the salt will not evaporate. This salt level should not adversely affect vegetables in aquaponics.
As your fish population grows in size, running an air pump, especially during the hot summers months and still humid evenings, will be a must. The warmer the water the less oxygen it holds, the bigger the fish the more oxygen it requires.
Quality fish food will assist in healthy, faster growing fish, look for pellets that are made in Australia and specifically for fish that you plan to eat.
Harvesting and Preparation For The Plate
For the crustaceans, it is kinder to sit them in ice slurry for about 10 mins, then spike through the back of the head, then boil or steam.
For fish, the quickest method is a sharp spike through the top to the head, or if you are quick and accurate a swift, heavy knock to the head will stun, prior to removing the head. Trout are slippery so best to have a glove or similar ready to get a good hold. Silver Perch will need scaling and beware of the spines on the underside and gill areas.
There are lots of great recipes for all the above, but I would encourage you to try them with little or no accompaniments to get a really good understanding of the flavor and texture. It should only take you 15minutes to catch, kill, clean and cook, you really can’t get much fresher than that.
Published in Garden Guru Magazine Spring 2012