Temperature/heater Question?

[rpgmomma8404]

My 15 gallon seems to be hold up at 80 degrees. I don't know what brand the heater is but it is a submersible. Seems to work great but I wonder if 80 is too much for a tropical tank?
 
Then my 10 gallon has a tetra whisper heater 5-15. The tank has been sticking around 77.9 - 78. Would that be too cold for Betta's? Also, I noticed that the tetra whisper heater light is suppose to go red when it is heating the tank but I've never seen it go red. The green light is on though so I figure it has to be working. I'm just concerned right now. I rather take back if there is a problem before getting fish. I've seen this heater in a lot of tanks for betta's. I looked at reviews and a lot were mixed. 

 

[neutron20]

Figure on 5 watts of heater power for every gallon of water you have. I would say that is warm enough for betta fish.. but come winter time is it going to be able to hold that?
 
the reviews were mixed? how so?

 

[rpgmomma8404]

Figure on 5 watts of heater power for every gallon of water you have. I would say that is warm enough for betta fish.. but come winter time is it going to be able to hold that?
 
the reviews were mixed? how so?

Read on different sites that it would break after a couple of months, possibility of over heating the tank or not heating the tank enough, then there were people complaining about it not even working out of the box. Good amount of the reviews were about how great it was for 5 to 10 gallon tanks or even smaller tanks.  

 

[rpgmomma8404]

First chilly night with the windows open and the temperature dropped from 78 to almost 69 degrees. I think I'm gonna take it back.