Can I keep five guppies in an unheated 12 Litre fish tank??

first of all, that's only about a 3 us gallon tank, IMO you shouldn't put more then 3 guppies in there

the only way not to have a heater, is when you can keep the water at a stable temperature of 78 degrees/26C at all times, which means night and day

if not yes you need definately a heater

If they were born in a cold water tank let's say at home, they would be fine...but if you bought them at the store where the water is warm then I would say no...I've kept guppies in cold water but that's only when their parents were raised in cold water...it all has to do with the easiest way for the fish to adapt to the environment...and if you got them from a store they will likely be susceptible to getting ich if you put them in a cold water tank.

depends. guppies need between 24 and 28 degrees so depends on how warm ur house it. and 5 will be fine as long as no more than 1 or 2 are male or you could have all male.

You could probably put a male Betta in with them. Betta are slower so the larger guppies should be fine, and the betta and will go for the small frys which would control the population.

Yep.

You can keep a labrador in a wendy house too, but it won't be at all happy in there.

Really, get rid of the jam jar and put living things in an environment that is good for them.

Fish ain't toys.

Don't treat them as though they are.

really depends on the temperature of your house-get a thermometer and see what it is and if it's a relatively stable temperature throughout the day and night.five is also a bit too many for a 12 litre tank.

I would say no. Our tank is always heated to the correct temp and ours live a happy life

NNNNNOOOOOO YOU CANNOT KEEP TROPICAL FISH IN A COLD-WATER TANK THEY WILL DIE YOU CAN ONLY TRANSFER COLD WATER TO TROPICAL UNLESS YOU KEEP THE TANK IN THE HOTTEST ROOM IN YOUR HOUSE

That is too small. Just because they don't die doesn't mean they are happy and healthy. We can live in closets as long as we have food right??????

not in an unheated tank no, as they are tropical they need the right temprature