I have a 20-40g heater in my 24g bio cube is this heater to large! b/c i have it set on the coldest setting and my tank was at 78 deg and when I turned it on in just a few hrs it went to 81 so i just decided to turn it off! any suggestion? maybe like a smaller heater or what should I do and this is running the tank with no lights!
78 deg is a good temp to keep. There is nothing wrong with having a powerful heater. Just set it to 76/77 deg. Having a large heater means you water will warm your tank quicker not giving the temp time to drop and stress your creatures/corals. My tank runs at a constant 76/78 deg because my pumps and lights keep it that temp. I have a 300w heater that never even turns on but is there for a fail safe.
1. Try going without a heater and see how much of a temp difference there is at night. My biocube stays in a good range at night with the 2 pumps generating enough heat to keep it warm. 2. Get a 50 to 100 watt heater. Hydor makes little flat heaters that do a really good job of heating water. 78 is ok but with the size or your tank if that heater sticks on your cube will fry. Take it from me i have almost Nuked my tank because of the heater and almost had a heater explode nasty stuff into my tank. Try it without a heater first.
I haven't used a heater in 10 years. I would opt for smaller ones in case of malfunction. A large one would heat up faster than you might catch it leaving you with nothing but dinner.
If you have a closed top, then you may not need a heater. My Red Sea Max is closed, and I haven't turned on the heater all winter. I do have a chiller for it, however.
For my 29 biocube I use a five gallon heater and I have it placed in the right hand side of the filter near the filter pads. I've never had a single problem with heat. Always stays at 78, and its not an eye sour in the display part of the tank.
I use heaters as well as chillers on my 29 gallon nano tanks. I used a stealth until I saw the recall on them. I now us an old glass 300 watter that was used on my old 125 gallon. It is placed in the outer center compartment that does not fluctuate in water volume of my JBJ Nano Cube
To the OP... If you had it set on its lowest setting and it heaed up past 80F without turning off, I think you have a stuck heater. No matter how big it is, if it is turned all the way down, it should surely shut off before it gets to 80.
