It really depends on three things; your currency (Im going to assume US dollars), the size of the aquarium, and the quality of heater you wish.
A decent quality heater for a moderately sized aquarium (20-30 gallons) will be appoximately $20-25 USD.
In general heaters cost around $15-40 USD depending on the variables discussed above.
Check out the heater section at www.bigalsonline.com And have a look at the Jager Heater line. I've attached a link.
The average price for a decent fish tank depends on the size. A typical 10 gallon glass tank will cost anywhere from $10-20, while a 20-gallon tank will go between $20-40. Prices go up from there.
Check your local pet store, depending on the wattage of the heater, you are looking at a cost anwhere from $7.95 to over $35.00
It depends what sort of fish you have (if their coldwater or not) it can range from about £15 to £100 mine was£55 from argos and it's been great!
Just use the element from your kettle! .. NO DON'T, go to the pet store where you bought your fish from and ask for their professional opinion. If anyone knows, they will!
The price can vary> I have a 75-gallon thermometer that cost 7 dollars. You can buy one from a price of one dollar up to over 15 dollars.
A heater can raise the temperature of a fish tank if needed
One can purchase a fish tank heater at various pet supplies shops. PetSmart, Petco, Marine Land, and Argos all have fish tank heaters for sale on their websites.
a big one!
Circulation
FIlter, heater, tank
If you have a heater, turn it off.
mine cost £70 pounds and it came with light, filter and heater
Usually there is a heater that warms the tank on purpose.
Most fish are around 78 degrees F.
The only thing that you can put in a tank that small is a betta fish or african dwarf frog. Tropical fish do better in a tank that is ten gallons or more. If the tank has a filter and heater you could put one guppy into it but that would be all and I doubt it has a filter and a heater.
It all depends on how much the tank holds and the wattage of your heater I like to have 10 wattage for ever gallon so if you hVe a ten gallon tan you need a 100 watt heater also the temperature of you want will make a deference normally my 20 gallon tank can go from 46F to about 77 F in two hours
you can put in sea snails and more brightly fish that you cant get with a heater in your tank