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? Goldfish are the most well-known coldwater fish in the aquarium hobby, so in this article, we’re going to cover 10 more cool species that can live without a heater.

1. Sunset Variatus Platy

Livebearers, or fish that bear young, have a special place within our hearts. However, we love the ease with which they produce baby fish. The sunset variatus platy (Xiphophorus variatus), has been one of our favorite fish over the years. They are a combination of all the best qualities you’d want in a fish.

It is available in a variety of colors and patterns. – They are very hardy and affordable. – About two to three inches in length. – Friendly and gets along well with other fish and plants. – Easy to breed for enjoyment

They can be kept at a wide range of temperatures with or without a heater. However, they prefer pH levels higher than 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

Because of its tiny size and bright red-orange fins, this nano fish is very popular in aquascaping. It can tolerate pH ranges from 6.8 to 8.8, moderate water hardness, and cooler waters. Also known as the galaxy rasbora, CPD, or Danio margaritatus, it has the reputation of being a little shy. However, given the right environment, you can often find the males circling each other in a dance off competition. You’ll be able to create a beautiful display in your planted tank if you have six or more of them.

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

3. Rainbow Shiner

Rainbow shiner (or Notropis Chrosomus, a native to the United States) is used to cooler waters. They are known for their brilliant purple and pink spangling, especially during mating seasons. 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. You should keep them in a school of six or more, which can be difficult since they’re a bit pricey and hard to source. If you have the money and are willing to wait for them to mature, they will be the most beautiful fish you have ever seen.

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

Are you looking for an algae eater? 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. Hillstream loaches enjoy eating Repashy gel food and good quality wafers. If you feed them well, you may see some breeding behavior, and baby aliens will start popping up all over the place.

Hillstream loaches may be aggressive towards one another. To spread any territorial or breeding behavior, you should either get one loach or three loaches in a group.

5. Endler’s livebearer

Poecilia wingsei is a smaller version its famous cousin, guppy. It has also been bred to have unique fin shapes and colors. The original wild-type Endler’s Livebearer is the best choice. They can survive at room temperatures with a pH range from 6.5 to 8.5. They are peaceful and blend well with other fish in the aquarium. A 10-gallon tank can be used to breed them. It should contain approximately two males as well as four females. You can quickly fill your aquarium with live plants, hiding spots, and you will soon have a factory of fish babies.

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

6. Clown Killifish

Another coldwater nano fish, the Epiplatys Annulatus killifish, can be kept together with small species in a community tank. They have striking blue eyes, their bodies are marked with wide vertical bands, and the males possess a tail that looks like a rocket flame (hence their other nickname “rocket killifish”). They swim high up in tanks, and like many other killifish, will often jump out of aquariums. 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.

Clown killifish can live up to three years if they are well taken care of.

7. Cherry Shrimp

Neocaridina davidi is a popular fish keeping species due to their bright colors and Skittles-like appearance. They also love eating leftover fish food and algae, which makes them very easy to breed (even in colder weather). You can easily purchase them at your local fish store or aquarium society auction, and sometimes even major pet store chains will carry them. For a 10 gallon aquarium, you can start with 10-20 shrimp. Make sure that they have enough calcium and other minerals. Soon, your tank will be filled with dwarf shrimp. Our complete care guide is available 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

You are looking for something bigger? Consider the dojo loach (also known as the weather loach or Misgurnus anguillicaudatus). The hot-dog-sized fish can reach 10-12 inches in length and should not be kept alongside smaller species such as the celestial Pearl danio or cherry shrimp. You can instead try varitus platy, barbs and other medium-sized fish that aren’t considered food. Dojo loaches have many entertaining behaviors. They can be seen digging in the gravel and scavenging food with their whisker-covered mouths. They are very affordable and will make a wonderful addition to any coldwater aquarium.

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

9. Barbs

While barbs love cooler waters, many have the reputation of being aggressive and can bite. There are several types of the rosy bar (Pethiaconchonius), such as neon, normal and long-finned. They can swim very quickly and are relatively peaceful so you can keep them alongside other community fish of similar size. Barbodes semifasciolatus (the gold barb) is more aggressive than rosy barbs. This species would work well with other barbs and dojo loaches. Both species grow to approximately three inches or more, should be kept in a 29-gallon or larger tank, and are quite entertaining to feed because of their hearty appetites.

Barbs can swim very fast and should be kept with six other people to reduce aggression.

10. White Cloud Mountain Minnow

Tanichthys Albonubes can be purchased as a feeder fish in pet shops, but they also make excellent beginner pets due to their ability to survive in nearly any tank size and temperature (aslong as it is 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. For fun, get 10-12 fish, and enjoy their simple beauty.

Many people keep these hardy minnows in plastic tubs outdoors during the warm summer months.

For more stocking ideas, see our Top 10 Lists!