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

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:

You can find them in many colors and patterns.

They can tolerate a wide temperature range, without or with a heater. Their preference is for pH levels above 7. 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. Also known as the galaxy rasbora, CPD, or Danio margaritatus, it has the reputation of being a little shy. 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 amazing in a planted aquarium and are often used to highlight aquascapers’ designs.

3. Rainbow Shiner

The rainbow shiner, or Notropis Chrosomus, is native to the United States. It’s known for its vivid purple and pink spangling and mating season. These torpedo-shaped fish reach 3 to 3.5 inch in length. They can be kept alongside other peaceful fish that are tolerant to similar water conditions. Because they are costly and hard to source, you should keep them in schools of six or more. You’ll get the best-colored fish if you have the finances and can wait one year for them mature.

The unusual purple and pink color of this native fish in the United States makes it difficult to find.

4. Hillstream Loach

Need an algae eater for your unheated tank? Look no further if you are looking for an algae eater for your unheated tank. The hillstream liach (Sewellia Lineolata), does an extraordinary job eating brown diatoms and green alga, and it looks strange, almost like an alien spider sucking on your glass. There are many varieties of similar loaches like the Chinese hillstream and butterfly loaches. Most of them prefer cooler water temperatures and pHs between 6.6 and 7.8. Hillstream loaches are fond of eating Repashy gel food, high quality wafers and other foods that sink to bottom of aquarium. If you feed them well, you may see some breeding behavior, and baby aliens will start popping up all over the place.

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 Lifebearer

Poecilia Wingei looks like a miniature version of the famous guppy. However, it has been bred with many different 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. Plus, they’re quite peaceful and mix well with many of the fish on this list. Set up a 10-gallon aquarium with at least two males and four women. 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 prolific and can easily breed in a planted aquarium with ample 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 swim high up in tanks, and like many other killifish, will often jump out of aquariums. Clown killer fish prefer a pH range of 6.5-7.5 with moderate water hardness.

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, Skittle-like colors, love for eating algae and leftover fish foods, and ease in breeding (even outdoors in cold weather). You can find them in your local aquarium society or fish store, and occasionally even big pet shops. 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. You can find our complete care guide here.

Neocaridina squid were originally brownish-gray. But, they’ve been bred into many different colors like red, yellow blue, orange and green.

8. Dojo Loach

Do you want something a bit bigger? Consider the dojo loach (also known as the weather loach or Misgurnus anguillicaudatus). This fish is hot dog-sized and can reach 10-12 inches long. They should not be kept alongside smaller species such as the celestial Pearl danio or 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’re fairly cheap for their size and make a great addition to any larger-sized, coldwater aquarium.

Dojo loaches often find their way into goldfish tanks thanks to their tranquil temperament and preference for cool water.

9. Barbs

Many barbs are great in cooler waters but often have the reputation for being fin nippers, so keep them in groups of six or more to minimize their aggression. There are many types of the rosy barb (Pethia Conchonius), including neon, long-finned, and normal. They can swim very quickly and are relatively peaceful so you can keep them alongside other community fish of similar size. Barbodes semifasciolatus is the gold barb. It’s a bit more aggressive than their rosy counterpart, and they will be happy with dojo loaches as well as other barb species. Due to their appetites, both species should be kept in a larger tank (29-gallon) and grow to around three inches.

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 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. Take 10-12 fish and breed them together 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.