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While this article is titled for cherry shrimp, please note that the information is applicable to all types of neocaridina (and most other shrimp), including but not limited to: fire red, bloody mary, red rili, blue velvet, blue dream, blue rili, carbon rili, blue jelly, blue pearl... Yeah, there are a lot of 'em...
There are two separate questions that need to be answered here:
The first is relatively straightforward to answer, while the second depends on what your goals are as a shrimp keeper.
If you prefer a video format, we also cover these topics on our YouTube channel!
Neocaridina are tough shrimp – some of the hardiest in the aquarium hobby, in fact. They can be shipped cross-country in freezing or scorching conditions (in an insulated container), be stuck at the post office for 5-8 days, then still arrive alive and well at your door. They have been known to survive at temperatures as low as 50°F (10°C) and as high as 90°F (32°C).
The key word in that last sentence is survive, though, because those extremes are not ideal. You certainly won’t see them posing with a Live ~ Laugh ~ Love sign at 90°F. They’ll be sweating their butts off, metaphorically speaking.
To keep your shrimp stress-free, it’s best to have your tank between the range of 65-85°F (18-29°C). Outside of those ranges, their growth rate, breeding rate, and immune system are all affected. Again, they may be able to survive, but they will not thrive.
In addition to maintaining a temperature within the stated range, it is also important to prevent rapid fluctuations. By rapid, I mean roughly a 5-8°F change in less than an hour. Stressful temperature fluctuations are more common in smaller tanks (5 gallons (19L) or less) and in rooms that are poorly insulated. That means you absolutely should not keep your shrimp in a cup of water in your garage—I will find you and make you re-read this article.
In summary, your shrimp need a heater if the room where the tank is kept goes outside of the recommended temperature range (65-85°F (18-30°C)) for extended periods of time. They also need a heater if rapid temperature changes are possible (e.g. by a window that gets opened frequently). If neither of those are possibilities, then you are free to save your money.
Now, is there a reason you may still want a heater in your tank?
Yes—depending on your goals as a shrimp keeper, a heater may be very beneficial.
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The first reason to have a heater in your tank is to ensure a stable temperature. The room may not normally go below 65°F (18°C), but what if the room heater stops working? Or what if abnormally cold weather occurs? Having a heater in your tank is insurance against events like those harming your shrimp.
The other reason is that temperature has an impact on a shrimp’s growth rate and breeding. According to a paper by Tropea et. al., neocaridina eggs take approximately 21 days to hatch at 24°C, whereas they take only 15 days at 28°C and 12 days at 32°C. After that, juveniles grow faster at higher temperatures—at least for the first 30 days—and are more likely to become pregnant after reaching sexual maturity. From this data, we can conclude that higher temperatures lead to higher (think explosive) population growth. More heat and shrimp do lead to some problems though, which we’ll discuss in the next section.
Densely packed colonies, combined with higher temperatures, often lead to problems with bacterial infections like rust disease. This is because a dense population often leads to worse water quality, which in turn causes bacterial infections. In addition, bacteria grow faster at higher temperatures and there are more shrimp to pass on infections when they occur. As such, it is important to perform more frequent water quality checks and water changes when your tank reaches its carrying capacity (approx. 8-10 shrimp per gallon) to avoid disease. Some shrimp keepers claim to be able to keep up to 40 shrimp per gallon, but it’s incredibly difficult to accurately count shrimp when they are densely packed and have plants in them (necessary to help with water quality at high densities) so there are few trustworthy claims for higher densities.
In addition to affecting growth rate, there are some articles that cite a study stating that temperature affects the female:male offspring ratio—a phenomenon known as temperature-dependent sex determination that is seen in some turtles and fish. Based on the results of the study, more females are born when the berried (pregnant) female is kept at a lower temperature. This would imply that turning your tank temperature down—slowly of course—would produce more females, which could then be grown quickly by increasing the temperature. Or perhaps have a secondary tank that you transfer berried females into while keeping the rest of the population in a higher temperature tank.
Well, it’s a cool idea… But it may not be true. I provide a more detailed discussion of the questionable methods used in this paper at the end of this article, as it may not be of interest to everyone. If you would like to learn more, then click here to skip to it now! Otherwise, simply continue onto the next section.
To summarize, you need a heater in your shrimp tank if the tank frequently gets below 65°F (18°C). for long periods of time or if the temperature fluctuates widely throughout the day. If, however, the tank stays stable and in the acceptable range, then you can have a perfectly healthy and stable colony without a heater.
On the other hand, if you want your shrimp to breed quickly so you can see a bunch of cute lil shrimplets—or if you want to breed them to sell—then getting a heater and setting it to 78-82°F may be best according to the paper mentioned previously. Just remember that a larger, faster growing colony has a faster metabolism, leading to more waste and the need for more frequent maintenance. If you are willing and diligent enough to keep up with proper tank maintenance, then our recommended heater for shrimp tanks is provided below:
The Orlushy Submersible Aquarium heater is a budget-friendly heater that has been working well in our tanks over the past two years. It has temperature control, a light to indicate when it’s working, and comes with a separate digital thermometer to double check that the temperature is actually where you set it to. Be sure to get the right wattage for your tank size!Pssst... Want to learn everything you need to know to have happy and healthy freshwater shrimp? We've got you covered with clear, concise, and fun information in every lesson of The Shrimp School!
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Please note that there is a slight decrease in the percentage of female offspring at higher temperatures in the Tropea study. It was not found to be statistically significant, but a study with a larger sample size may find a difference. Therefore, the evidence for temperature-dependent sex determination in neocaridina is inconclusive. We know it's not very satisfying, but that's science for you sometimes. We'll be on the lookout for new papers published on the topic and updated this section when more information becomes available.
Thanks for reading and happy skrimpin'!
