I bought a Marina 17w heater last week, and when I was testing it out, I noticed that the light didn't even go on, and it certainly didn't heat the water. I was testing it in a bowl full of lukewarm water. Right now I have a Marina 10w in my fish's 2 gallon which doesn't warm the water enough, and I am planning to get a 3 gallon tank next week. I'm bringing the 17w Marina heater back to the store and intend to swap it for a 25w elite heater. It doesn't have an adjustable thermostat, so I'm worried that 25 watts might be too much for a 2 or 3 gallon tank, even though it's suppose to stop heating when the water reaches a certain temperature. This is the heater I want to get: http://www.petcetera.ca/Products/Fish/Heaters/Elite-Submersible-Pre-Set-Heater-25W.aspx Would this be ok? I want to put it in his 2 gallon first so he gets used to it before transferring him to the new 3 gallon tank.
If the 25W is not adjustable, it will be too much for your little tank. Yes, they have internal thermostats, but all heaters works along with the ambient temperature in the room. A 25W could quickly overheat such a small tank. I'm a larger tank person so I always use my adjustable 50W and turned them down to 76. That has always given me a steady 80 in both of my 2.5 gals. The 25W would be okay if it were adjustable. I tried a non-adjustable 10W in one of my 2.5gals and it must've malfunctioned. Within 48 hours it was 86 degrees! I quickly opted for an adjustable.
Wow, my 10w heater is not adjustable either and only keeps his tank at 25 Celsius (around 75 Fahrenheit). But the top of his bowl is open so I think a lot of the heat escapes through there. The tank I'm getting will have a lid, so I need to take that into consideration. I can't find small adjustable heaters anywhere around here. Do you think I should stick with the 17w for when I get the 3 gallon tank?
Many people have great luck with the smaller, non-adjustable heaters. I wish I could help, but I'm not very experienced at smaller tanks. I only use my 2.5gals for QT tanks when I buy new bettas. So the 50W adjustables work great for the few weeks I need them - then I use them for the new 10gals I set up. I have limited knowledge and what I know about 2.5gals, I've already shared. On a long term basis I'm not the expert. I'm sure others will step in. Lots of folks have your exact set up and many years at non-adjustable heaters. :)
I had a 25W Tetra heater, but it was defective so I brought it back and got the Marina 10W. I'm going to the city next week Tuesday, so I'll be doing some shopping around at different stores. If all else fails, I was thinking of trying a Tetra heater again, (hopefully a working one this time). It does say for 2 to 10 gallons on the package.