10 Best Coldwater Fish that Don’t Need A Heater

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? The most popular coldwater fish in aquarium hobby is the goldfish. In this article we will cover 10 other cool species that can survive without heaters.


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.

You can find them in many colors and patterns.

They can be kept at a wide range of temperatures with or without a heater. However, they prefer pH levels higher than 7.0. They will love to be mixed with the other fish listed on this page.

Variatus platies come in a huge variety of colors and patterns and are very fun to breed.

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 of 6.8 to 8.0, moderate water hardness, and of course cooler waters. It is also known as the Danio margaritatus or the galaxy rasbora. The males can dance off each other if they are in the right environment. Keep them in a school of six or more, and you’ll have a stunning display for your planted tank.

Celestial pearl danios look stunning in a planted tank and are often used by aquascapers to highlight their designs.

3. Rainbow Shiner

The rainbow shiner, also known as Notropis Chrosomus, is a native American fish that is used to cooler water. It is well-known for its bright purple and pink spangling during mating season. These torpedo-shaped fish grow to 3 to 3.5 inches long and can be kept with other peaceful fish that enjoy similar 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.

These native fish from the United States are hard to find, but worth it for their unique purple and pink colors.

4. Hillstream Loach

Need an algae eater for your unheated tank? You don’t need to look any 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 many varieties of similar loaches like the Chinese hillstream and butterfly loach. Most of them prefer cooler waters with a pH of 6.6 to 7.8. Hillstream loaches enjoy eating Repashy gel food and good quality wafers. You may notice some breeding behavior if you feed them properly, and you will see baby aliens popping up all around the aquarium.

Hillstream loaches can be a little aggressive with one another, so either get one loach by itself or at least three in a group to spread out any territorial or breeding behavior.

5. Endler’s Livebearer

Poecilia Wingei looks like a miniature version of the famous guppy. However, it has been bred with many different colors and fin shapes. 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. Plus, they’re quite peaceful and mix well with many of the fish on this list. You can breed them by setting up a 10-gallon tank that contains approximately two males, and four females. The aquarium should be filled with live plants. There should also be plenty of hiding places. Soon, you’ll have a factory full of fish babies.

Endler’s livebearers have a very high breeding rate and can easily reproduce in a well-watered aquarium.

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”. They are a bit like other killifish and will swim towards the top of your tank. Make sure you have a tight fitting lid to stop them 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, also known as Neocaridina davidi, are very popular among fish keepers due to their bright colors that look like Skittles, love for eating algae and leftover fish foods, and easy breeding (even outdoors in cold weather). They can be purchased at any local aquarium society auction or fish shop. Sometimes, even major chain pet stores will have them. 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. Our complete care guide is available here.

Neocaridina shrimp are originally brownish-gray, but they have been bred to many colors such as red, yellow and orange.

8. Dojo Loach

Are you looking for something larger? Consider the dojo loach (also known as the weather loach or Misgurnus anguillicaudatus). The dojo loach is a hot dog-sized fish that can grow to 10-12 inches in length. It should be kept separate from smaller species, such as celestial pearl daanio and cherry shrimp. Try the variatus platy and barbs instead. These fish are not edible. Dojo loaches display many fun behaviors, such as scavenging for food with their whisker-covered mouths or burrowing into the gravel. 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 slightly more aggressive than the rosy bar. They would be able to live with dojo loaches and other barb species. 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 are very fast swimmers and should be kept in a school of six or more to lessen any 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). These minnows are sometimes called “the poor man’s neon tetras” due to their low price. However, they can be found in many varieties, including albino, long-finned, and golden. 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.

For more stocking ideas, see our Top 10 Lists!