how many watts to heat my betta fish tanks?

[Any Huit]

Hi all!

I'm thinking about buying new heaters for my two betta fish tanks, a 5 gallon and a 10 gallon. Currently, there is a 25w heater for the former and a 50w heater for the latter. But lately, I've noticed that they aren't keeping the water temperature above 70F (in the 5 gallon) and not above 74F (in the 10 g). Neither one is adjustable, they're at a preset temperature of 78, but the mercury thermometers (the stick ones, not digital) don't seem to agree.

So my question is, do you think in your experience it's worth buying new heaters, and if yes, should I double the wattage? so increase from 25w to 50w for the 5g and 50w to 100w for the 10g? I always thought that the rule of thumb was 5w per gallon, and I don't want to accidentally electrocute my bettas 🤯

Also, if yes, do you have any brands to recommend? I was thinking this time to get adjustable heaters with digital thermometers built in.

always thankful for your patience & ideas!

a betta mom

 

[cavdad45]

I generally go 5watts/gallon. Others say 3, but why overwork the heater, causes premature failure.

[AllFishNoBrakes]

I have a 25 watt in my 4 gallon tank, and I do 50 watts for my 10 gallon tanks. I keep my house at 70° year round. 
 

I like the Orlushy heaters and I’ve gotten all of mine on Amazon. They’re easy on the wallet, have worked well with me, and they include a digital thermometer. I think I’ve replaced 1 in the 2+ years I’ve had tanks.