See how someone was able to turn their backyard swimming pool into a crayfish farm, to grow red claw, in the suburbs of Melbourne.
by Iain Harrison ACS Tutor from 1984 to 2001
A friend of mine in a Brisbane seaside suburb became tired of paying for chemicals and cleaning his pool, especially as he seldom it. He thought of draining and demolishing the pool, but then realised it would be very expensive to get large equipment inside his backyard to do this, and he would also likely damage the fence and garden. He would also have to remove the concrete used to build the pool, and refill the hollow with soil.
Then he got the bright idea of converting the pool into an outdoor aquarium and thereby turning a liability into an asset. Initially Silver Perch were introduced but they quickly died due to inadequate space and so were not replaced.
He then decided to turn the pool into a Red Claw Crayfish ‘Tank’.
The pool was a conventional one of approximately 10 m by 3m and 1-2m deep (containing approximately 50,000 litres of water). Before the “conversion”, the pool cost about $40/month to maintain. For a on-off cost of $50 he converted it to meet the crayfish’s requirements.
The pool was left stagnant for two months to get rid of the chlorine and to let the algae grow (as food for the new occupants). The algae also provides a protective cover for the Red Claws to hide from predators such as birds.
Red Claw Crayfish Requirements
Red Claw (Cherax quadricarinatus) are a native freshwater crayfish with the males having a distinctive red patch on each of the large claws. The body is generally (but not always) a blue-green colour. They grow to about 500 grams, with the tail meat being approximately 25% of the total body weight.
Licensed Red Claw farms range from Cairns in Queensland to Taree in NSW, ie. tropical and subtropical areas. The ideal conditions are:
A water temperature range of 23-31oC
A pH range of 6.5-8
Dissolved oxygen levels over 5 mg/L
The pool water should not exceed the range of 10 o C to 35 o C.
Adults Red Claw are omnivorous, eating a variety of plants (including ornamentals put into the pool as decoration and as crayfish shelter) and fresh animal material. Chicken pellets can be used in small quantities so that they are eaten before they decay and pollute the water.
Under ideal conditions, Red Claws can grow from 5-10 grams as juveniles, up to 70-80 grams (just big enough to eat) in 12 months. My friend initially stocked his pool with two thousand 2-3 cm juveniles for a cost of $300. In hindsight, he realised he should have only started with 1000 juveniles to prevent overcrowding and cannibalism.
He found that the water level needs to be maintained at about 10-15 cm. below the edge of the pool. This means topping up the pool in summer and draining some water out of it after heavy rain. If the water gets much higher than this, especially in wet weather, then the crayfish will “go walkabout”. On at least one occasion my friend found a “stray” 150 metres away at a neighbour's house.
In addition to the crayfish, hardy aquarium fish were introduced into the “extended” aquarium. These rapidly bred and are now minor cash flow projects with the excess being sold to local aquarium pet shops. They are easy to catch with a fine net, especially if they are used to being fed regularly (eg. catching them as they feed on small pieces of bread which float briefly before being eaten).