10 Best Coldwater Fish That Don’t Need a Heater

Most freshwater pet fish require an aquarium heater because they’re used to tropical temperatures, but did you know there’s a whole class of coldwater fish that are perfectly fine at room temperature? We’ll be covering 10 more coldwater species in this article. Goldfish is one of the most well-known aquarium fish.

1. Sunset Variatus Platy

Because they are so easy to make baby fish, livebearers hold a special place for us. But, over time, the sunset variatus plate (Xiphophorus variatus), is one of our favourites. They combine all the things you would want in a perfect fish:

– Available in a huge variety of colors and patterns – Very hardy and inexpensive – Only two to three inches long – Lively yet gets along with other fish and plants – Easy to breed for fun

They can live in a broad range of temperatures, with or without a heater, and they tend to prefer pH levels above 7.0. You’ll fall in love with them when you mix them with other fish and live plants.

Variatus platies are fun to breed and come in many colors and patterns.

2. Celestial Pearl Danio

This nano fish is quite popular in the aquascaping world because its golden spots and red-orange fins make it look like a tiny brook trout. It can tolerate pH between 6.8 and 8.0, moderate water hardness, as well as cooler waters. It is also known as the Danio margaritatus or the galaxy rasbora. However, given the right environment, you can often find the males circling each other in a dance off competition. Keep them in a school of six or more, and you’ll have a stunning display for your planted tank.

Celestial Pearl Danios look amazing in a planted aquarium and are often used to highlight aquascapers’ designs.

3. Rainbow Shiner

As a native of the United States, the rainbow shiner (or Notropis chrosomus) is definitely used to cooler waters and is known for its brilliant purple and pink spangling, especially during mating season. These fish can grow to 3 to 3.25 inches in length and can be kept together with other peaceful fish who enjoy the same water parameters. They should be kept in a group of six or more because they are expensive and difficult to find. You’ll get the best-colored fish if you have the finances and can wait one year for them mature.

This native fish to the United States is difficult to find, but it’s well-worth it because of its unusual pink and purple coloration.

4. Hillstream Loach

Need an algae eater for your unheated tank? Look no further. The hillstream locach (Sewellia liolata) is not only an excellent eater of brown diatoms green algae but it also looks very unusual. It can be seen sucking on the side glass of your glass like an alien stingray. There are several types of similar loaches, such as the butterfly loach and Chinese hillstream loach, and most of them tend to enjoy cooler waters and pH from about 6.6 to 7.8. Besides snacking on algae, hillstream loaches love to eat Repashy gel food, good quality wafers, and other foods that sink to the bottom of the aquarium. If they are fed well, you might see some breeding behavior and baby aliens may start appearing all over the aquarium.

Hillstream loaches are a bit aggressive and can get a little territorial with each other.

5. Endler’s Livebearer

Poecilia wingei is like a smaller version of its famous cousin, the guppy, because it also has been bred to display many unique colors and fin shapes. However, if you get the original, wild-type Endler’s livebearer, they are very hardy and can live at room temperature with a wide range of pH from 6.5 to 8.5. They are peaceful and blend well with other fish in the aquarium. To breed them, just set up a 10-gallon tank with approximately two males and four females. Fill the aquarium with live plants and lots of hiding spots, and soon you have a factory of life, bursting at the seams with fish babies.

Endler’s livebearers can be very prolific and will readily breed in a planted tank with lots of cover.

6. Clown Killifish

The killifish (Epiplatys anulatus) can also be kept in a tank together with other small fish. Their eyes are strikingly blue and they have vertical stripes on their bodies. The males have a tail that looks like it is a rocket flame, hence their nickname “rocketkillifish”. Like many killifish, they tend to swim at the top of the tank, so make sure your aquarium has a tight-fitting lid to prevent them from jumping out. Clown killifish like a pH between 6.5 and 7.8 with moderate water hardness. They will lay eggs in floating plants, or a spawning mop.

Unlike some killifish, clown killifish are not an annual species and can live about three years or more if well cared for.

7. Cherry Shrimp

Neocaridina davidi are very popular among fish keepers because of their bright, Skittles-like colors, fondness for eating algae and leftover fish food, and ease of breeding (even outside in cold weather). These fish can be bought at your local aquarium society auction and some pet shops chains. You can get 10-20 shrimp to fill a 10-gallon aquarium. Once they are established, ensure that the water has enough calcium and minerals. Before long, you will have a swarm of dwarf shrimp. You can find our complete care guide here.

Neocaridina Shrimp were initially brownish-gray. However, they are now available in many colors including red, yellow, orange, green and black.

8. Dojo Loach

Looking for something a little bigger? You might be interested in the dojo locach (also called the Misgurnus anguillicaudatus) This hot dog-sized fish can reach 10 to 12 inches long and therefore should not be kept with smaller species on this list, such as the celestial pearl danio or cherry shrimp. Instead, try the variatus platy, barbs, and other medium-sized fish that won’t be seen as food. Dojo loaches are known for their playful behaviors such as digging into the gravel or scouring for food with their whisker-covered faces. They’re fairly cheap for their size and make a great addition to any larger-sized, coldwater aquarium.

Dojo loaches can often be found in goldfish tanks due to their calm temperament and preference for cooler waters.

9. Barbs

Although barbs can be great in cooler water, they are often known for their aggressive nature. Keep them in groups of six to eight to reduce aggression. There are many types of the rosy barb (Pethia Conchonius), including neon, long-finned, and normal. These fish are quick swimmers and relatively calm, so they can be kept with similar-sized community fish. The gold barb (Barbodes semifasciolatus) is a little more aggressive than the rosy barb, so they would do well with other barb species and dojo loaches. They can grow up to three inches and should be kept in a tank of 29 gallons or more. Their large appetites make them quite entertaining to feed.

Barbs swim fast and should be kept in a group of six or more to minimize aggression.

10. White Cloud Mountain Minnow

Tanichthys albonubes is often sold as a feeder fish at pet stores, but they make great beginner pets because of their resilient ability to survive in almost any tank size and temperature (as long as it’s not too hot). Because of their affordable price, these minnows have been called the “poor man’s neon Tetras”. They are available in many different varieties such as long-finned, golden, and albino. You can get a group of 10-12 fish and breed them for fun.

Many people breed these hardy minnows outside in large plastic tubs during the warmer summer season.

If you enjoy articles like this, check out our Top 10 lists for more fish and plant stocking ideas!