Welcome to FishLore! Yes your tank needs a heater if you have any tropical fish. You need a heater (or heaters) that will efficiently keep your tank around 78 degrees. To determine the amount of wattage you need, think 5 watts per gallon. That would be a 50 watt heater for a 10 gallon tank. When you start getting into bigger tanks like 55 gallons, it's better to divide your wattage into more than one heater. This will make the temperature in the tank more uniform.
my acquarium is 50 gallons., what but it has divider.., coz' the other side has 5 parrot fish., and the other is 3 molly,5 swordtails,4tigerbarb., do i need to seperate the tiger barbs?? sow my fish will going 2 mate? tnx for teaching me.., fishlore is a big help.... i buy a trhermometer mr.. and 1 hour ago.., the result is 82 F is it ok? :-* tnx!! ^_^
82 degrees is probably fine, but might not be preferred by all your fish. If you can get it down to 80, that would probably be better. Since you are using a divider, I would recommend a 250 watt heater for each side of your tank.
Also, I think your tank is overstocked. The parrot fish really need all of your tank. In my opinion, 25 gallons for 5 parrot fish is not enough. Have you tried allowing all the fish to swim together? How attached are you to the smaller fish?
ah..,so 250 watts.,, tnx for answering my questions.., really? overstocked? maybe.., but my parrots are babies..!! they are small.., so it is ok..,?? i did not try.., coz' the shop here said the parrot and molly,barb,tail are not compatible.., so i did not try it anymore.., i have 2 50 gallons but the other tank is occupied by my lovable flower horn... flower horn is great fish.., it puts away ur stress..,,, hihi., now he is 2 yrs. old..., very bulky!! Tongue