As winter continues to creep closer, Dr. Nate Storey of Bright Agrotech is answering a few of your questions about cold weather aquaponics. More specifically, he'll take questions on:
- Fish response to colder temperatures
- Appropriate temperature ranges for tilapia
- Best type of heaters for IBC aquaponic systems
"My fish seem to not be eating as much these days. As the temps drop in my fish tank, will the colder water change the fish’s eating habits?"
It is quite common for fish to slow down when the water gets cold and that leads to lower production as well. As a result of your fish slowing down, there will be fewer nitrates in your solution so you don’t want to overfeed. Its one of those things you'll need to keep an eye on and make sure you're feeding appropriately.
If you don't already, I would recommend figuring out some way to heat your tanks. This way when the weather cools down you won't decrease your production.
What kind of temperature ranges are most appropriate for tilapia?
Tilapia are definitely warm water fish.
There is a reason they are the most common fish in aquaponics. For starters, they're very tolerant of poor water quality and they eat almost anything you can feed them. Some folks use traditional fish food, while others choose to supplement this type of feed with duckweed. Heck, you could probably feed them grass clippings if you want. But, while they'll eat just about anything, the issue with tilapia is that they're very temperature sensitive. Remember, these fish are primarily coming from Africa or other historically tropical environments.
For most tilapia, when the water temperature drops down to about 55 degrees, they will go into a stress induced dormant state. You'll know this is happening because one day you'll walk in and those tilapia will be bumping into the walls and swimming around like they're drunk.
As you can imagine, this isn't a great state for your fish. It's actually really dangerous for their biology. Once your water temperature drops down to 50°F you've probably killed them.
There are very few tilapia varieties that can withstand those types of temperatures.
I have played around with various hybrid species before as well. There's actually a hybrid called a Rocky Mountain White that's tolerant of cooler temperatures; supposedly this is a fish that can get down around 50°F without croaking.
I've also played with some tilapia varieties that aren’t supposed to be cold tolerant at all, like the Nile-based Florida Reds. I say Nile-based because there's almost no truly pure stock. What I've found is that often times the hybrids that are bred for cold tolerance are just poor feeders and gain weight slower than most. I prefer fish that will feed voraciously up until the time that they die over fish that are tolerant of lower water quality.
I will say that exposing your fish to more extreme variables over time, they will adapt. We've got a number of generations in our system at Bright Agrotech and I'd be willing to bet that they could occasionally tolerant water temperatures down in the high 40's.We've got this crazy mutt tilapia breed now that seems to tolerate the almost all the abuse we throw at them.
However, if you're just starting off with tilapia that you order through the mail or get from a friend, you need to keep those water temperatures above 60°F minimum. And, if you want good production, you're need to keep your temperatures between 70°F and 85°F.
"So the optimal temperature for tilapia is 70 to 85 degrees Fahrenheit. Is that correct?"
That’s where you're going to get maximum production.
"What is the best type of heater for an IBC system during the cold months?"
There is a wide array of heaters out there for standard IBC aquaponic systems. However, perhaps the best design I've seen was on the Aquaponic Gardening site.
This simple and effective design featured only a thermostat and stainless steel water heater element. I think it would be a really great kind of emergency heating technique.
There are many DIY designs out there and of course, there are some commercial products as well. I don’t necessarily have an opinion on some of the commercial designs simply because I've never used them, although I've heard some negative reviews about some of them that make me question whether they're really worth the money.
Definitely go on the Aquaponic Gardening site and search ‘homemade heater’.
There will be some results that come up for stainless steel water heater element base heater and I think it's a really great way to heat.
Wood Burning Boiler Heating
If you've checked out our furnace video, you'd see that we heat our fish tanks with a series of heated coils coming from our wood furnace.
Now, every system is different and you have to heat your system with the resources specific to and appropriate for your area.
Commercial growers, although backyard hobbyist as well, need know what's the cheapest fuel and the easiest way to deliver heat to their system.
This sometimes requires a little creativity by the grower to devise an appropriate way to heating their systems.
In Bright Agrotech's aquaponic system, we already have these great hydronic coils that deliver hot water from our boiler system to our heat exchangers bringing warm air into our vertical farm during the cold months.
Making the decision to heat our fish tanks with these coils was not only inexpensive, it only required installing a three-way valve onto the tubing. I think it only ended up costing us a couple hundred bucks in tubing. At the end of the day, it allows us to heat our fish tanks with practically zero additional input from us because of the low tech nature of it all.
While this works well for our application, grower's need to design and choose their heating system based upon what resources they have available.