My landlord has just informed me that there will be interruptions to electricty tomorrow for about one to two hours. I am sure my betta will be OK without a filter for that length of time, but what can I do to keep him warm. I'm concerned about how the drop in temperature will affect him. He is in a ~5 gallon bowl at present with a 25W heater keeping him at around 77 degrees. I do have a smaller tank available too. Would the heat be lost quicker from a larger or smaller tank? Should I wrap his bowl up in towels or something?

One or two hours isn't too bad.I would think that the tank that he's in would be the one to keep the temp the longest. He should do okay,just keep him away from drafty areas.Does his tank have a light that you can turn on if needed? That would probably help a bit with temps.

1-2 hours should be fine. To answer your questions, you will lose heat faster in a smaller bowl, so keep him in his regular tank (if that's larger) and using a towel for insulation won't hurt either, but I wouldn't worry unless you can't count on your landlord being precise about 'just 1-2 hours'.. good luck

Thanks guys,
He is away from drafts anyway. I think I'll probably place a towel over the top of the bowl at least as it losses quite a lot of heat from there I think (It has no lid).

um Devs, he does have a light yes, but the electricity will be off...

How about placing a big beam flashlight outside of his bowl and leaving it right next to the tank and for the time the power is off. Might heat the tank up some. not a regular size one but one with the big round beam

Yeah, I agree. Provided it's only a few hours I think he's better off staying put in his own bowl (moving him would be more stressful in the short term). They give another warm (for April!) day for most parts of the UK again tomorow so I'd suspect what with ambiant room temp and all, you'd probably not see a drop of temp in his bowl of more than a couple of degrees over a couple of hours anyway which is tolerable. Using a towel or something for extra insulation is a good idea though

Well Archimedes seems to have survived the electricity being cut off and is showing no adverse affects. The power was off two days in a row for a short time. I don't actually know how long for because I was at work, so I don't know by how much the temperature of his bowl dropped either. I placed a towel over the top of the bowl with a small part uncovered. When I came home the second night the temperature of his bowl was 82F rather than the 77F he's normally kept at, so it actually worked a little bit too well.
Anyway, he seems fine.
Thanks for your advice.

I'm pleased things went OK. We had a similar situation at home yesterday as the electricity company were due to come and put in a new electricity meter. They said the electricity would only be off for 20 minutes and to make sure you unplug any sensitive equipment beforehand. I was worried about the filters being off for any long period of time and the potential for any surge damage to the lights and UV thingy etc. after the power went back on so I unplugged them, but things went fine and it actually only took them 15 minutes to do it all. I was worried about the possibility of 20 minutes turning into hours and hours though, you know how these things go sometimes