Many of us in the freshwater fishkeeping hobby have been taught to keep our aquariums between 72 and 80 degrees Fahrenheit. Some fish need warmer water, but others will thrive between these temperature ranges. Many fish are considered tropical and need warm water to be successful in an aquarium. Others are more tolerant of both warm and cooler water temperatures. When researching fish stocking for an aquarium, it is important to learn which fish can be kept under what conditions. This article will discuss a handful of fish that can be kept under cool water parameter conditions, likely not requiring a heater.
Aquarium heaters aren’t always used to maintain warm water temperatures. At times, they are used to keep water temperatures stable. If your home has fluctuating temperatures, it might be a good idea to keep an aquarium heater running to assist in reaching stable water parameters. Check out the 6 Best Aquarium Heaters for Freshwater & Saltwater Fish Tanks to see a handful of different companies that make heaters to help warm your aquarium water or help keep your water temperatures stable.
1. White Cloud Mountain Minnow
Many newcomers in this hobby have likely seen or heard of White Cloud Mountain Minnows. They are often suggested to new fish keepers because of their hardiness, beautiful colorations, and active personalities. White Cloud Mountain Minnows are also excellent options for aquariums that do not run heaters. They do best in cooler water conditions, and it’s recommended to keep them between 65-75° F. White Clouds come in two varieties. You can find “normal” White Cloud Mountain Minnows and the “gold” version, which is essentially an albino version of the fish. Both types are gorgeous options for a planted aquarium.
If you’re shopping for these fish online, consider purchasing White Cloud Mountain Minnows (affiliate link) from TheShrimpFarm. Also, check out the White Cloud Mountain Minnow – Complete Care Guide to learn more about this fish.
2. Zebra Danio
If you’re looking for another incredibly hardy, active fish that does well in cool water, look no further than Zebra Danios. They tolerate water temperatures between 65 and 75° F. Calling them active is an understatement. Zebra Danios spend most of their time moving throughout the aquarium. They do best in groups of at least 6, but more is always recommended. Zebra Danios are not as flashy as many other freshwater fish but have unique horizontal stripes running across their body.
The Zebra Danio is a fairly common fish that can be found at fish stores. They come in silver and gray colorations, albino, and Glofish® has a colorful line of Zebra Danios.
3. Guppy
Anyone who has kept freshwater aquariums likely knows about Guppies. These fish come in an assortment of colors, are generally easy to keep, and are quite active. They are quite tolerant of many different water temperatures and will succeed in aquarium water temperatures between 65 and 82° F. From experience, most people do keep them in warmer water, but it should not be challenging to acclimate them to cooler aquarium temperatures.
For those of you who have not kept guppies, use caution because these are live-bearing fish. They produce live offspring instead of laying eggs and are prolific breeders. If you let these fish breed without intervention, your aquarium may slowly get overrun with Guppies.
4. Rainbow Shiner
Rainbow Shiners are cold-loving freshwater fish. They will do great in aquariums with temperatures as low as 60° F and as high as 72° F. They do best in cooler waters that are highly oxygenated. In the wild, they are found in slow to moderately moving streams, which bring ample oxygen from the surface. Rainbow Shiners’ colors change throughout the year. During the breeding season, the colorations on this fish are incredible. You’ll see them with an array of blues, pinks, and purples. However, they do lose quite a bit of color outside of their breeding season.
This fish species does best in groups of at least 6 individuals. They are social fish and do a fair amount of interacting when kept in larger groups. Check out their behavior in the beautiful stream aquarium.
5. Paradise Fish
Paradise Fish are gorgeous freshwater fish that come in an assortment of colors and can do great in a cool water aquarium. There are a few different species of Paradise Fish, but each species is a Gourami. Like other Gouramis, Paradise Fish have a labyrinth organ, which allows them to breathe air from the surface. Paradise Fish do well in aquarium temperatures ranging between 64°F and 78°F.
Use caution because Paradise Fish are known to be semi-aggressive to aggressive. Larger and heavily planted aquariums may help mitigate some aggression, but they are more than happy to terrorize an aquarium. Each person who has kept Paradise Fish likely has a different experience with them, because each fish has a unique personality.
6. American Flagfish
American Flagfish are fantastic algae eaters and very tolerant of cool-water aquarium setups. This fish species will do perfectly fine in tanks with temperatures between 66 ° F and 75° F. American Flagfish can display some aggression when kept in an enclosure that is too small or overpopulated, or during spawning periods. Otherwise, they are usually fairly peaceful and do not bother other tank mates. I recommend keeping them in small groups. If possible, they should be kept in a ratio of 1 male to 2-3 females.
7. Medaka Ricefish
Medaka Ricefish, also known as Japanese Ricefish, are fantastic nano fish for no heater aquariums. They do great in temperatures between 60 and 75°F. Medaka Ricefish should be kept in small groups of at least six individuals. A small group should have no issue being kept in a 10-gallon aquarium or mini-pond. This is because they should not grow more than 1.5″.
TheShrimpFarm has Galaxy Medaka Ricefish (affiliate link), which are white in color with a vibrant blue around their eyes. However, you can find Japanese Ricefish in different shades and colorations.
8. Dojo Loach
Like many other Loaches, Dojo Loaches exhibit a noodle-like appearance when they’re small. As they grow, they begin to change shape and look more like a hotdog. Their unique appearance goes perfectly with their interesting personalities. They often sleep on their side, bulldoze through the aquarium, and do other weird things. They’re really enjoyable fish to keep and do best in fish tanks with temperatures ranging between 65 and 75°F. Dojo Loaches do best in aquariums with a softer/rounded substrate that they can burrow into. They’re also considered escape artists and do best in fish tanks with well-fitted lids.
9. Hillstream Loach
The Hillstream Loach is a fish with a unique appearance. It has a flattened body to handle the fast-flowing streams of its natural habitat. These fish are gorgeous with black and yellow patternwork throughout their bodies. Reticulated Hillstream Loaches should not be kept in aquariums warmer than 75°F, but can be kept in temperatures as low as 64°F without issue. They can be fantastic tank mates for Rainbow Shiner, in appropriately sized fish tanks.
You can often find Reticulated Hillstream Loaches (affiliate link) for sale on TheShrimpFarm. They’re fantastic fish to keep in a properly designed enclosure. They will spend much of their time consuming algae and detritus on rocks and other surfaces, but should readily accept most foods provided.
10. Goldfish
If you have a very large aquarium or an outdoor pond, then Goldfish might be the right cool-water fish for you. Fancy Goldfish such as the Ranchu, Ryukin, and Oranda usually do great in temperatures between 68 and 78°F. Common Goldfish are often kept in outdoor ponds with fluctuating temperatures and seasons. If you decide to choose these fish, you have to understand that they get massive and are incredibly messy. They do best in larger volumes of water with excellent filtration to keep up with their waste production. Learn more about Goldfish by looking at the Goldfish – Complete Care Guide.
Final Notes
There are many cold-water enjoying fish out there, but these are my favorite choices based on shape, color, and behavior. This list is purely opinion-based, and other fish keepers may have different choices for their favorite coldwater freshwater fish. Let me know if you have experience with any of these fish or have a fish that you think should have made this list. Lastly, this list is in no particular order. Each fish is great in its own way.