Faulty Heater ? Any Suggestions

How are you measuring the temperature, what type of thermometer? The stick on ones that go on the outside are not very accurate as they are affected by the air temp as well as the tank temp. The cheapest, good-enough type is the tube with liquid inside that sticks with a sucker to the inside of the glass.

Heater thermostats are notorious for not being terribly well set. It is always best to ignore the actual number on the heater and go by the water temp - provided the the thermometer is accurate. Adjust the heater a bit at a time over a few hours to get the temp you want. If you ever need to increase the temp (eg if the fish get whitespot, raised temp is part of the cure) make a note of the setting before turning the heater up.

Take it slowly with fish in the tank. The temp should only be turned up or down by 1 deg C in 24 hours.

  No heater on! i did turn it off briefly, but panicked incase it got too cold, my heater is reading 23, but the thermometer say 26 c is that too warm do you think? will leave it at that for a day or so anyway.

Mmm room temp is not constant, some times central heating on, overnight none, so your saying leave heater on at 23 it will cut out above that,  and if it keeps reading 26 not a lot i can do about it 

Thanks Richard, will leave it as it is overnight, and turn it down tomorrow when i can monitor it. Mmm alwasy something to fret about, inherited an unwanted small guppy, cos he was being picked on, now the little bugger is nipping at my platies, back to LFS tomorrow i think : (

Good grief woman!

You only need one heater in there so take the other out. Set the one you're leaving in to 26 and then leave it and go to bed. You're fish will be fine.

edited to add: all your kit is new, you'd have to be very unlucky to have 2 heaters that dont work. The thermostat should kick in when temp drops below the level you've set it at.

Some people advocate a two heaters approach. The theory is that by having two lower powered heaters you are protected to a certain degree from one becoming faulty, i.e. if one stops working, the second would try to compensate and at least stop the temperate from dropping significantly, whilst if one suddenly goes hyper and tries to superheat the tank, it shouldn't have enough power on it's own to cook the fish. I'm not sure how well this works in practice though and it probably would be best sticking with one for the time being anyway until you get the temp stabilised.

The simplest way to set a heater is to start slightly too low (fish won't mind for a day or two) and turn it up a tiny bit at a  time, waiting a at least a couple of hours between, until the thermometer reads what you want. Then ignore the actual number on the heater dial.

You can always remove the heater from the filter, buy a heater bracket and put the heater somewhere else.




It's not just tank heaters that have badly calibrated thermostats. A few years ago, I had to have the thermocouple in my oven replaced. The repair man said I'd have to learn to cook with it all over again as the temp it gave would be different from the old one at the same setting on the knob.

As long as your ammonia and nitrite stay at zero, once a week is fine for water changes. And since you only have a few fish, 10% would be more than enough for now. But increase the amount a bit every time you get more fish. Once the tank is fully stocked, 25 to 30% a week is about right.