Keeping your aquaponics system productive throughout winter shouldn’t present too much of a challenge for those living in temperate zones. Unless you are in a frost-prone area, your vegetables should still be growing well.
Seafood varieties you can grow at home
If you grow rainbow trout, then winter is a very exciting time. Trout thrive in water temperatures of 14 to 18 degrees Celsius, but are still comfortable down to 5 degrees Celsius and up to 24 degrees Celsius. Throughout their growing season, trout will eat ravenously all day if you let them. With regular feeding they grow from a 10cm fingerling to a plate-sized fish in just one winter. They are fast living, fast eating, fast growing, but also fast to stress if water quality and oxygen levels are not right. Having clear, filtered water with lots of splashing (and preferably an additional aerator) is important to ensure healthy, happy fish.
Marron are also quite happy in cooler water, with much the same required temperatures as trout, however both are carnivorous so it is better not to have them in the same tank. To get marron to grow large they need to be kept separated from the opposite sex, as once they breed they will stop growing. If you have ever wondered why your marron haven’t grown very big, they have probably been busy doing other things! There is no size limit to the marron you grow at home, so if you want to clear out and start again, eating them at a smaller size is quite acceptable.
Silver perch differ as they will slow down their food intake as the water temperature drops. They will survive winter, but they just won’t grow through this period.
Growing vegetables with your fish
The more you feed fish, the more waste they produce, so you need to make sure your grow beds are planted out well and your vegetables are taking advantage of the extra nutrients. Planting fast-growing varieties such as silverbeet, spinach and chard will greatly assist in taking up these excess nutrients. An alternative is to plant English watercress into baskets and float it on the pond surface. Trout don’t eat plants or algae, so if you are growing this fish then your floating plants will cohabit fine. The downside is you may have to spend a bit of time over winter pulling out algae by hand.
If you are in a frost-prone area, you should consider putting a small pop-up greenhouse over your vegetables. This should save you from any losses you might ordinarily experience.
Winter aquaponics maintenance
During the cooler months, beneficial bacteria don’t populate anywhere near as quickly as they do during summer, so bear this in mind should you decide to do a big cleanout. As a rule, winter is a great time to clean out ponds and water filters, as most fish have slowed down their activity and eating. However, if you are growing a thriving population of trout, be careful and do small cleans regularly.
Should your water quality get out of balance or your trout show signs of fungus or stress, you need to act quickly. Test the water for ammonia and if that is present change at least half the water in the tank. The first and best indicator of sickness in trout is showing no interest in eating; the second sign is hanging around the surface of the pond. We recommend you pump out at least one third of the water and add 3kg of pool salt per 1,000 litres directly into the tank, then fill it back up slowly over the next couple of hours. It may seem drastic, but a salt treatment will usually rectify the problem if you act quickly. This amount of salt shouldn’t have any detrimental effects on your plants.
If that doesn’t turn them back into happy fish within 24 hours, you may need to repeat with a higher level of salt. This time add an additional 3kg per 1,000 litres (to make it a total of 6kg per 1,000 litres). With this level of salt you will need to turn off the water going to the growbed. After two to three days, or when you think the fish are back to normal, you can do small water changes to bring the water slowly back to fresh. At that time you can turn your water back on to circulate through your vegetables. Don’t forget if you’re using fresh tap water you must de-chlorinate it with water conditioner. If you are using bore water it’s a good idea to oxygenate it before adding it to the pond, as it doesn’t have much oxygen when taken straight from underground.
Using quality fish food specific to the fish you want to grow is really important. Quality feeds are designed to maximise the growth and the health of your fish and are less likely to foul the water. The best fish foods are made right here in Australia, so seek them out.
Learn more about growing your own seafood at home here with our video from The Garden Gurus.
Images: Calinda Anderson
About the Author – Calinda Anderson
Calinda runs the Woodvale Fish and Lily Farm, established over 18 years ago and now a leader in the water gardening industry. The farm produces a fabulous display of water lilies, water plants and fish, and the friendly, knowledgable staff can always offer advice and assistance. Calinda is also passionate about aquaponics and enjoys sharing her knowledge with people wanting to learn more.
For more information, visit www.woodvalefishandlilyfarm.com.au