The Effect of Temperature on Aquarium Plants

Written by: Tammy (@aquarist_tl) and Team Buce Plant

Most planted-tank owners know the basics of how to care for and manage the aquatic plants in their aquariums. The general knowledge for aquatic plant care being that most plants need a stable combination of light, CO2, and nutrients to do well underwater. An interesting variable in this process that is not usually discussed is temperature. 

Will aquarium plants die in cool water? Does temperature affect plant growth? Do aquatic plants prefer warmer water or cooler water? 

This article will go over the role that temperature plays on the plants in our aquariums. 

Can Aquarium Plants Survive in Cooler Water?

Since many of these aquatic plants come from tropical areas, it could be assumed that these plants would prefer warmer conditions. A very common temperature that aquarists keep their aquariums at is about 78F (~25.5C). Most aquarium plants do well at this temperature if they are kept in their ideal conditions (e.g. sufficient CO2 level, a good source of light, enough nutrients). They are able to grow and propagate at steady rates in most aquariums. However, these same species of plants do not have these stable conditions in nature. 

If we go back to their roots (pun intended) and look into their natural habitats, we will see that a great majority of aquarium plants are found on the sides of rivers, lakes, or other bodies of freshwater. In these areas, the water level will fluctuate according to the season, so sometimes the plants are underwater and sometimes they are out of it. 

Water holds its temperature a lot better than air, meaning the temperature of water will be more consistent. As the day turns to night and night back to day, the temperature will be swinging from high to low with it. The average temperature range in tropical areas falls between 70F-85F. The plants out of water will especially be going through these big swings, yet they are still able to grow and prosper. While every plant is different and has its own unique set of ideal conditions, it is safe to say that most aquarium plants can survive cool water conditions of 70F-72F. Arguably, they could do even better at these lower temperatures.    

The Effect of Temperature on Plant Growth and Planted Tanks

Like all living things, plants have a metabolic rate. A plant’s metabolic rate can be defined as the speed in which the chemical processes that take place within the plant occur for it to survive. In simpler terms, it can be seen as how fast the plant photosynthesizes and grows. 

Metabolism is affected by temperature, so temperature does play a role in the growth of aquarium plants. Heat increases the metabolic rate, meaning that the hotter our aquariums are, the faster our plants will grow to a certain degree. On occasions where it gets too hot, the plants will do poorly and may even die. The speed of which our plants are growing can actually change the way they look. When grown in hotter conditions, some species of plants will grow more compact because the heat is causing them to flower quicker. 

Plants like water wisteria can grow more compact depending on the intensity of the light and temperature.

If an organism is growing faster, it will need greater amounts of the resources it requires to metabolize. For aquatic plants, this means that faster growth increases the demand for CO2 and nutrient uptake. Knowing this concept, we can use this knowledge in the maintenance of planted aquariums. 

In typical tropical aquariums, the heat is kept at a constant temperature that is set by a heater. If you were keeping a planted tank housing Discus or other fish that prefer high temperatures (82F-86F), you may find some of the plants in those aquariums to be struggling. This could be because the plants are not getting a sufficient amount of resources to prosper. Since they are being kept in warmer temperatures, they will have a greater need for nutrients and CO2 to keep up with their metabolic rate. In high temperatures, consider slightly increasing the amount of CO2 injected into the aquarium and also the amount of fertilizer added. This may aid the plants that look like they’re struggling. Buce Plant offers a variety of CO2 products as well as fertilizers like the UNS All in One Plant Food to help your plants grow! 

Similarly for aquariums keeping fish that prefer lower temperatures (70F-72F), it is possible that you could be oversupplying the tank with CO2 and ferts. Plants in cooler water will grow slower, and therefore do not require the amount of resources that they would in warmer water. These excessive amounts of metabolic resources could lead to algae issues, so try lowering the amounts of CO2 and ferts if you’re having algae issues in low temperature tanks. 

Cool vs. Warm

While many of the aquatic plants we have seen and own can tolerate temperatures up to 84F, most species do better in cooler water (low 70s). Hot temperatures (above 84F) may kill plants that prefer colder temperatures like tiger lotuses and bucephalandra. Plants in cool water have a much more steady metabolism than those in warmer water. The lower temperature decreases the amount of CO2 and nutrient uptake needed by the plant, and the assimilation within the plant is more organized.

Another benefit to cool water is that it can hold more dissolved gases than warmer water, which means CO2 and O2 have more potential to stay available within the water for the plants and livestock to use. Therefore, plants should be having a much easier time flourishing in temperatures of 70F-74F. If you’re looking into setting up a planted tank that falls within this temperature range, consider getting some freshwater shrimp as livestock! They do well in cooler water and love picking and eating organic materials provided to them from aquatic plants. Amano shrimp in particular are especially great for planted tanks since they are one of the best algae eaters in the hobby!

Temperature is often an overlooked parameter of our aquariums, but it has the potential to impact the growth and survival of the plants and animals living in them. Hopefully this article will serve as a reminder of the importance temperature can play in planted tanks, and also adds to the growing knowledge of the aquarium hobby! 

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