Backyard Aquaponics
A place to discuss aquaponics

My Barra pond gets over 30c on warm days and during that time I'm running constant flow. The Barra love the high water temp and are growing fast. But with the higher water temps I've noticed the plants are struggling despite all the water they want being available. Is the water too hot for the plants?

Craig

Hi Craig - my experience is that it is plant dependent. Lettuce will all bolt. Corn will grow like wheat! Most plants will perform somewhere in between. I suggest you plant according to the recommendation for the season. It also helps to experiment with a few varieties for different veggies.

tank temperature & % of oxygen in the solution (ppm) water temps
10ºc (50ºf) 13 ppm

20ºc (68ºf) 9-10 ppm

30º (86ºf) 7 ppm

As you can see the oxygen content in the resolution approximately halves for every 10ºc rise in solution temperatures.

As a direct result of the water temperature being at higher temps the plants will need more oxygen at the roots so the problem is almost squared and there is 25-40 % less oxygen in the solution and the plants will need double the amount than normal.

Roots are unable to work effectively, leading to:
a build up of toxins meaning that the plant will be unable to take up the water and feeds needed for healthy growth
The whole plant begins to deteriorate as photosynthesis and carbohydrate rates slow leading to wilting.
Leaf damage and root die-back. Ethylene is released and causes a toxic overdose and the roots fail.

Shamelessly copied and pasted,but it does a good job of explaining,Ideal temps are in the 18-22c range.

If you flood and drain instead of continuous flood, then the roots will have access to a lot more Oxygen. Evaporation will cool the media too, if it isn't exposed to intense sunlight.

I've had lettuce, tomatoes & basil all happily growing under 2 weeks of 44C+ weather here in Adelaide. Didn't even wilt even under direct sunlight. My water topped out at 32C during that period.

With the lettuce though, it depends on a few factors like the species of lettuce. I've got some henderson black seeded, and they just bolted after a 40+ day, while the cos lettuce & butternut crunch are happily growing away.

I usually go by, if the fish can handle it, the plants can too.

But a bigger water volume will keep temps more stable.