Vanessa Monge Augusto Fernandes 's Profile
- Joined: 03/02/2011
- Last Updated: 10/02/2011
- Location: Gold Coast , Queensland, Australia
- Climate Zone: Sub-tropical
- Gender: Female
(projects i'm following)
My Permaculture Qualifications
- PDC course
- Type: Permaculture Design Certificate (PDC) course
- Teacher: Geoff Lawton
- Location: Permaculture Research Institute
- Date: Oct 2007
Turning your swimming pool into a fish farm using the Silver Pearch(Bidyanus Bidyanus)
We have approximately 3 kilos of Silver Pearch and 4 kilos of small native fish in our pool.Swimming pools are ,if run along traditional lines unproductive,poisoness enviroments,that cost upward of 2500 dollars per year to maintain.
We decided on Silver Pearch because it was commonly available and extensive research had already been done over many years,it is also a native fish in Australia,originally found in the Murry darling basin but now threatened in the wild.There are regulations and they are strict on what spiecies are allowed to be kept by Aquaculturists.The centre that has produced much of the research is the Department of Primary Industries research station in Grafton.
We live about 4 hours drive from the DPI and have visited it on a couple of occasions to meet with the scientists and tour the facility.A few months back we recieved information that due to the commercial industry which is worth 51 million dollars a year,not requireing further study that the centre may be mothballed.With peak fish fast approaching and growing world food shortages, you would think governments would continue to sponsor this vital research for the sake of food security.
The mothballing is still conjecture at this stage,so sanity may still prevail.We were impressed by the passion and dedication of the researchers and also with the facility it self.Our humble little swimming pool is a funky little low tech lab and it is a far cry from the DPI.
Above is a stocking density for farm dams,you just need to scale it down,to pool size.So many variables determine the amount of fish that a body of water can support that a good deal of reading should be done before you embark.
I can recommend Nick Romonowski who has produced some great books that are easily digested and targeted to the interested ameture or professional.The Design Manual has a chapter devoted to Aquaculture and gives a simplistic framework on extensive aquaculture,and intensive aquaculture and names a number of useful spiecies that are unfortunately illegal in Australia.
Our pool has no mechanical aeration,so we treat it as an "extensive" aquaculture system rather than an "intensive "one.Intesive by definition means energy inputs such as mechanical aeration,introduced food supplies,such as pellitized formulated foods and pumps and filters to help polish the water,they usually do not have plants and fish in the same enviroment,commercial fish farms are an example of this.Aquaponics could be seen as a form of intensive aquaculture,as could channel and cage systems which have high monitoring and labour inputs.Intensive also means extreamly high yields,one researcher we spoke to was working on a cage system that could with adequate inputs grow to plate size 100 fish per cubic meter of water in 9 months,so thats an impressive case.Aquaponics is gaining lots of popularity in Australia,with a number of skilled people promoting it.For those with a bit of time and money it's obviously a way of creating a bit of food security,provided the system is autonomous of the ""system""...ie stand alone solar and back up pumps,food supplies you can generate on site such as soldier fly lavae,vegtable wastes and worms.
A big problem in the past has been,the edibility of some spiecies of fish including Silver pearch,even though Silver pearch is omnivorous,eating both zoo and phyto plankton as it ages it tends to eat more on the phytoplankton so sometimes they aquire a "muddy taste"we have a cheap and easy home grown method of purging this taste.
We use a 60 litre black plastic drum and an aquarium pump for oxygen and gradually add a solution of salt water,no more than 3% of the total water over a number of days and then feed them on brown bread while in the purging bin,this process can last for 3-7 days,you could comfortably have 3 fish of 200 grams in this system.We also flush the bin periodically with fresh unclorinated water about 30% volume after the first 3 days.
The fish pictured took nine months to grow and was fed on zooplankton and phytoplankton that was generated from compost that came from the pool originally (see earlier post)as well as the other sources of nutrients found in the pools plants system.It's weight is 200 grams.
With a little effort and when we have the available funds and time to really concerntrate on this project we will endevour to up the productivity of the fish system in this polyculture by incorporation of pumps and filters run on stand alone solar.
We encourage all pool owners to go down this track,if the system is kept basic like ours and is planted out with approximately 30% of the surface are in plants and not overstocked with fish or over fertilized you can enjoy a good swim as well.It took about 18 months to get it to what we call a steady state.The water stays relatively clear and clean and if algal blooms form the are easily delt with by the addition of more plants or the physical removal of the algae.We spend about 1 hour per month on this housekeeping.
Some general rules when starting are small steps introduce each element slowly,plants,nutrients,fish all situations in Aqua culture are site specific.
You can see our dog,"the garbage guts" in the back ground standing infront of our food forest,on this day he had eaten a rat,about 20 cherry tomato,kang kong and should a poor fish ever pop it's head up to snatch a bug on the surface of the water "garbage guts" will eat him as well.We thought bird predation would be our biggest problem but the dog seems to keep the cormorants away,and eat their fill for himself.
Geoff Lawton spoke once of making sure that the system had nowhere for a cormorant to dry it's wings and then they won't fish your dam,makes alot of sense to plant your system out with thick borders to prevent evaporation as well from wind and sun.Our dog probably does a good job of this.In farm dams predation by birds can be up to 50%!
We have installed some bamboo on the western edge in the hope of lessening these two evaporative effects