Heater for 30 gallon cichlid

[Potluck]

I've never really bought Marineland stuff but this heater had really good reviews, it's for my 30 gallon cichlid tank I took away from my nephew that neglected it, I think it's 30 gallons I will have to do measurements to see but I'm not exactly sure how to do that, my question is how do I do the measurements to find out if it is indeed a 30 gallon and if this heater is decent one, in the store it was 45.00 I got it in Amazon for 22

 

[Potluck]

UPDATE, it's 20 I guess I should have did the measurements before I got the heater

 

[coralbandit]

A 30 gallon [standard] tank is 36X12X17H aprox.
A 30 breeder is 36X18X13H aprox.

This will help if you have something different...
Aquarium Volume Calculator (W.C.S. Ltd.)

 

[coralbandit]

Heaters are best measured by how many degrees above the room temperature you need to raise the aquarium...
This chart may help...
http://www.aqueonproducts.com/assets/008/11515_165wh.jpg

 

[Potluck]

Yeah my nephew told me the people that he got it from was 30 it's not its 20, just worried about it over heating the tank, kind of bummed cause i was going to redo the stocking because my nephew went out and bought fish he didn't know anything about so there's a convict and an mbuna in there, the mbuna is in bad shape from getting beat on and I think the convict is too big for a 20 gallon but I'm not sure.

 

[coralbandit]

A heater that is too large will not over heat your tank if it is working properly...
What will happen is it will turn on and off too many times[too often] and have a shorter service life .

 

[Potluck]

Well I have to turn it on 77 I had it on 79 the temp went up to 83, with to small of a heater it has to work harder to maintain 80 degrees so I guess they would both wear out quite frequently