Help! Prob With Biorb Heater And/or Thermometer

What kind of thermometer are you using?
The kind that stick on the outside and change colour are not terribly reliable because, being on the outside, they can be affected by the air temperature of the room. The kind that go inside the tank with a column of liquid are better, and also digital ones. I see that the heater pack includes the 'column of liquid' type.

It does seem odd if the temp still went up after turning the heater off. Silly question, have you turned the central heating up so the room is very warm?

As for a replacement heater, how long is the heater that is designed for the tank? There are a few makes that are short - I looked into them when I needed one for my quarantine tank. What is the maximum length your biorb can fit in it?

The cheapest thing to try first is to get a thermometer, one of those that goes inside the tank with the liquid going up a grid. That should tell you if the problem is a thermometer malfunction rather than a heater problem.

Should you need a new heater -
I have a Visitherm 25w heater in my betta's tank which is 18cm long. I used to have a Sera heater in my quarantine tank which was the same length - Sera say on their website that they are short and easy to install in small tanks. This heater was rather old when it finally started to leak - and had probably been abused going in and out of the QT.

I know, fishkeeping is supposed to be a relaxing hobby. And it is, when things are going well.

But when things aren't, and you're worried about your fish it can be really stressful.

Good luck. Hope you figure it all out soon.

And next week they are turning the electric off for the best part of the day - what on earth do I do then!

There's a nice article here which offers good advice for when you have a power outage.

How long will the electricity be off? Last year mine was off all day and my 3 tanks came through with no problems.
Using a battery powered air pump will keep the water circulating and this should keep your bacteria alive. They are nowhere near as delicate as was thought when that article was written. I joined Thinkfish in 2006 (the old version of the site, not the current one which has only been going a couple of years) and the articles were all there then. I would put the tank end of the air line (sea chest ornament, air stone, whatever you choose) on top of the substrate.
Or, maybe push the air line tube underneath the rocks without disturbing them too much. You could do that in advance so any mess has time to settle, then connect it up to the pump just before the power goes off.

If you can move the tank to a room which can still be heated, do that. If not, wrap the tank in something as the article says.

Because this is a planned power cut, you can feed the fish more lightly for two or three days, then don't feed at all the day of the power cut. This means less ammonia will be going into the water on power cut day. Feed lightly again for the next day or two.

Keep an eye on the ammonia and nitrite levels for a few days until you are sure the filter has come through OK. If you do see either or both above zero, you'll be going through a mini-cycle. It won't last long, just do water changes as necessary.

Feed lightly for a couple of days before the cut, and a day or two after. And nothing on the day itself.

It is scary. But take heart from the fact that my fish were all fine