Ideal Temperature and Light Conditions for Fish

Silver Perch

As we're entering the hotter part of summer, it's important to consider how fish in aquaponics systems will cope with the increased water temperature. Because fish are cold blooded, it is hard for them to adjust to a large range of water temperatures. A steady temperature within their tolerance speeds up their growth and aids in protection against disease. Check out our post on Fish Species for Aquaponics for the ideal temperature for your fish.

How to protect fish in hot temperatures

In summer, water temperatures often rise above 25C around Brisbane. This is entering the danger zone for Perch and there are a few steps that should be taken to protect them.

1. Ensure there is adequate aeration - with higher temperatures there is less oxygen available to the fish.  A rate of aeration between 5 and 8 litres per minute for every 1000L of water should be used as a guide. An Aqua One SR7500 (360L/hr) or SR9500 (400L/hr) running two air stones is generally considered satisfactory for an single tank IBC aquaponics system.
2. Shade the tank, and if building a system consider partially sinking the tank into the ground.
3. Keep the fish tank clean by siphoning or vacuuming out any sludge.
4. Remove algae build ups.
5. Do not overstock fish - a maximum of 20kg per 1000L is recommended.
6. Consider a backup aeration system in case of a power cut.

Ideal Light Level for Fish

The light level should be reduced far enough to prevent algae growth, however not complete darkness. Incomplete darkness, fish are startled by the sudden light when a tank is opened or uncovered. Ideally, shaded direct light is the best compromise between algal growth and preventing fish stress. We also recommend harvesting or grading fish in darkness to reduce stress levels.