Temperature plays a crucial, yet often overlooked, role in planted aquariums. While tropical plants can survive in temperatures above 30°C (86°F), most species exhibit better health, form, and coloration in cooler water. Higher temperatures make tanks significantly more susceptible to algae, with Green Dust Algae being one of the most common culprits.
The optimal temperature range for most aquariums is between 22 and 26°C (72 to 79°F). We recommend maintaining tanks at around 24°C (75°F) to strike the best balance between plant growth, fish health, and minimizing the risk of algae. Cooler water also contributes to tank stability, as slower plant, microbial, and algal metabolism leads to more consistent conditions over time.
At temperatures above 26°C (79°F), it becomes harder to saturate the water with CO2, as gas solubility decreases with rising temperatures. This can hinder plant growth, as CO2 is a crucial component for photosynthesis in aquatic plants.
What Can You Do
In cooler climates, raising the temperature is easy, thanks to affordable and widely available aquarium heaters. However, in warmer regions, lowering the tank’s temperature can be more challenging. There are three main methods for cooling a tank, each with its own pros and cons:
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Fan: Aquarium-specific fans that attach to the tank rim can lower the temperature by a couple of degrees, depending on the room’s ambient temperature and humidity. Every degree counts, so this option is worth trying, especially in slightly warmer climates.
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Aquarium Chiller: Chillers tend to be expensive and can often be the most costly part of an aquarium setup. They also require a powerful filter or separate pump to function properly. Additionally, chillers can heat up the surrounding area in the room and are often noisy, particularly the more affordable models.
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Air Conditioning: Air conditioning offers the most consistency and convenience but comes with higher electricity costs. When combined with a fan, it can lower tank temperatures a couple of degrees below the set temperature on the air conditioner.
Lighting choice also plays a significant role in tank temperature. Metal halide and T5 lighting systems generate much more heat than LED units, so switching to LED lighting can help reduce heat buildup in the aquarium.
What About Cooler Temperatures?
While tropical plants can survive in water temperatures below 20°C (68°F), most species experience significantly slower growth at these lower temperatures. Additionally, this range is outside the comfort zone for most tropical fish, and some species become more susceptible to diseases like white spot.
For most planted aquariums, the sweet spot lies between 22 and 26°C (72 to 79°F). Maintaining this range not only promotes tank stability but also enhances the form and coloration of both plants and ornamental fish, creating a vibrant and healthy aquarium.