I have a 54 litre/12 gallon coldwater tank which fish should i buy?

guppies are good and they multiply really fast. some are very color full too. go to a fish store. there are lots of great varieties angel fish are pretty too. zebra fish and algae eaters are good too. good luck. I hope your tank is beautiful.
No tropical fish, unless you intend to buy a heater.
Pet stores will tell you which fish to get.
Algae eaters like warm water.
Barbs. Danios. Also, goldfish. A very good site for more information is provided below.
now, by coldwater you mean a tank that has a filter, a light, but no heater correct? that isn't really

a 12 gallon is too small for a goldfish, too small for danios, just about enough room for white cloud mountain minnows, but thats it that's readily available at fish stores really.

buy a heater and your stocking options go from 3, to potentially dozens!

first step, you need to cycle your tank, check the link below. do not add fish before you tank is cycled!

i gather you're a beginner? if so, after you've invested in your heater, you could get a group of male guppies, they're the prettier ones, but if you start to get females in there too, you're going to end up with so many babies coming out your ears you won't know what to do with them. this also goes for platys and mollies (mollies grow too large for a 12 gallon). everywhere stocks guppies as they are more prolific than rabbits, but be aware due to their extensive breeding they're no longer very hardy.

other potential fish for a cycled 12 gallon are listed below, but i don't mean put them all in together! take these names and go out and research anything that takes your fancy BEFORE you buy! try to stick to fish that grow to no larger than 2" when adult.

Honey Gourami
Sparking Gourami
Dwarf Gourami (beware, these are no longer hardy either)
Neon Tetra
Penguin Tetra
Glowlight Tetra
Cherry Barb
Hasbrosus Corydora
Pygmaeus Corydora
German Blue Ram Cichlid
Endlers Livebearer (wild guppy)
Pandy Corydora (can be delicate)
Otocinclus (mature tank with algae only)
you might want to get a heater for that sucker, or else one goldfish!! goldfish are the common coldwater fish but need 20-50 gallons a piece when they are full grown. get a heater, get up to 72 degrees and get some colorful fish like tetras, or a tank of swordtails, mollies, platys.. if you get tetras you also can a betta in there for the centerpiece...and no it wont kill all your fish. and yes it thrives in bigger water!
id stick with community fish...all tetras or a mix of mollies, swordtails, and platys.and always remember one inch of fish per gallon...youre not going to want any more than 10 fish at the most!!
and make sure to do a 25% water change each week with a gravel cleaner!! adding water conditioner and a teaspoon of sea salt per gallon will help out too!
Cold water tanks can be rather limited as far as stocking goes... You could maybe squeeze a -single- fantail or other fancy variety goldfish in there, but I think there are better alternatives definitely.

One option would be White Cloud Mountain Minnows or one of the various danio (Danio rerio) species. These fish can be adapted to cold water conditions just fine. Many species of barbs can also be kept in temperatures from the mid sixties and up. A Chinese Hillstream Loach would be another choice, however I think it may be a bit large for a 12 gallon, as well as prefering a tank with a strong current that replicates its natural river environment.

Hope this helps!
The most common coldwater fish is the goldfish, followed closely by it's larger counterpart, the Koi. However there are many other interesting fish that do not require a heated tank. Many coldwater fish are large enough that are only suitable for ponds. Since you are planning to set up an aquarium, I've put together a list of fish that are small to medium in size.
Barbs - Several readily available species of Barbs are tolerant of temperatures into the mid sixties, or even lower. All are easy to care for, and are suitable for a community aquarium. They include: the Gold Barb (Barbus schuberti), the Green Barb (Barbus semifasciolatus), the Rosy Barb (Barbus conchonius), and the Two Spot Barb (Barbus ticto).
Bloodfin Tetra - Both the standard Bloodfin (Aphyocharax anisitsi), and the False Bloodfin (Aphyocharax dentatus) tolerate temperatures as low as the mid sixties.
Bloodfins are offered in many pet shops, are easy to care for, and are quite hardy. They are active top dwellers and are best kept in schools.
Buenos Aires Tetra (Hemigrammus caudovittatus) - Easily found for sale, they will tolerate temperatures into the mid sixties. Standard varieties, as well as albino variants can be found. Like the Bloodfins, they are undemanding and easy to care for. They are suitable for a community tank, but will eat live plants voraciously.
Croaking Tetra (Coelurichthys microlepis) - Not often found for sale, they are an attractive fish that is worth shopping around for. Like other coldwater tetras, they are easy to care for and are suitable for community tanks.
Guppy (Poecilia reticulata) - As readily available as any fish, there are many attractive variations of this popular fish.
Hillstream Loaches - Although they are not often seen in pet shops, some species can be found for sale from time to time. Not all of them prefer cool temperatures, but most will tolerate temps that fall into the mid to upper sixties.
Native Fish - A variety of North American native fish are now being sold in the aquarium trade. Virtually all of them tolerate cool water. Availability varies from state to state, as do laws regarding which species may be legally kept in home aquariums. Keep in mind that some will become too large to keep in a standard aquarium.
Pearl Danio (Brachydanio albolineatus) - Like the zebra danio, this fish is very hardy and easy to care for. It will tolerate temperatures into the mid 60's without difficulty, and is easy to find. They are larger than zebras, but need not be kept in schools.
Weather Loach (Misgurnus angullicaudatus) - Readily available, this loach is one of the easiest to care for. Couple that with the fact that it will tolerate temperatures into the fifties, and it makes an excellent candidate for a coldwater tank.
Wimple (Myxocyprinus asiaticus) - Also known as the Freshwater Batfish. Not commonly found, it is an unusual fish that is worth tracking down if you like to have something unique. It will tolerate temps into the mid sixties.
White Cloud Mountain Minnow (Tanichtys albonubes) - One of the easiest fish to care for, a new gold colored variant has become very popular. They do best in cooler temperatures, although very low temps will lessen their attractive coloration.
Zebra Danio (Brachydanio rerio) - Outside of goldfish and the guppy, the zebra is the most readily available of all coldwater fish. They tolerate temps that fall into the mid sixties, and are very easy to care for. Long finned species are available, as well as a popular leopard spotted variety.
There are many other coldwater species I could cover, but the above list should give you enough options to get started. Good luck with your coldwater aquarium

Related Questions and Answers ...