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 …


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

We have a special place in our hearts for livebearers (or fish that bear live young) because of how readily they make baby fish, but over the years, the sunset variatus platy (Xiphophorus variatus) has become one of our favorites. They are a combination of all the best qualities you’d want in a 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. Mix them with live plants and other fish on this list, and you’re sure to fall in love with them!

Variatus platies can be bred in a variety of colors and patterns.

2. Celestial Pearl Danio

The nano fish is very popular in aquascaping because of its red-orange fins and golden spots. It can tolerate pH of 6.8 to 8.0, moderate water hardness, and of course cooler waters. It is also known by the Danio margaritatus, CPD or galaxy rasbora. If the environment is right, the males will often dance off with each other. 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 torpedo-shaped fish grow to 3 to 3.5 inches long and can be kept with other peaceful fish that enjoy similar water parameters. It is best to keep them in a small school of six or greater, as they can be expensive and difficultly 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 United States native fish is hard to find but well-worth the cost because of their unusual purple and pink coloration.

4. Hillstream Loach

Do you need an algae eater to heat your tank? Look no further if you are looking for an algae eater for your unheated tank. The hillstream loach (Sewellia ligneolata), not only does an incredible job at eating brown diatoms, green algae, but also looks quite unusual, looking like a tiny alien stingray sucking on your glass. 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 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 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. They’re peaceful and can be mixed with most of the fish on this page. A 10-gallon tank can be used to breed them. It should contain approximately two males as well as 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 are very prolific and will easily breed in a planted aquarium with plenty of cover.

6. Clown Killifish

The killifish (Epiplatys anulatus) can also be kept in a tank together with other small fish. Their striking blue eyes are accentuated by their vertical markings and their tails resemble rocket flames, which is why they are called “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 prefer pH 6.5 to 7.8 and moderate water hardness. They will lay eggs in floating plants or on a spawning mat.

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). These fish can be bought at your local aquarium society auction and some pet shops chains. Start with 10 to 20 shrimp for a 10-gallon aquarium, make sure they have enough calcium and minerals in their water, and soon you’ll be overrun with beautiful dwarf shrimp. For more information, check out our full care guide here.

Neocaridina shrimp were originally brownish-gray in appearance, but now they’ve been bred into many colors, such as red, yellow, blue, 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 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. Instead, try the variatus platy, barbs, and other medium-sized fish that won’t be seen as food. Dojo loaches display many fun behaviors, such as scavenging for food with their whisker-covered mouths or burrowing into the gravel. They’re fairly cheap for their size and make a great addition to any larger-sized, coldwater aquarium.

Dojo loaches are often found in goldfish tanks because of their peaceful temperament and matching preference for cooler water.

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. The rosy barb (Pethia conchonius) comes in many varieties, such as normal, neon, and long-finned types. They are very quick swimmers but relatively peaceful, so you can keep them with other similarly sized community fish. 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. 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 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). Sometimes known as “the poor man’s neon tetras” because of their inexpensive price, nowadays these minnows come in many strains, such as albino, golden, and long-finned. 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.

You might enjoy these articles. Check out our Top 10 lists to see more ideas for stocking fish and plants.