How to keep a betta tank warm without a heater

Same fish, new story. My betta fish Bud is in a 3.5 gallon tank with a filter and heater. Today I came home from school to find the heater broken and Bud much less active than normal. Usually he's constantly moving and swimming around through his plants and decoration, but today he wasn't swimming much and he was swimming very slowly.

His water temperature is only at 22-23°C right now. I can't afford a new heater until Friday.

How can I keep his tank warm until then?

Note: I am doing daily water changes(possible fin rot, different thread, don't want to risk it going entirely untreated just in case he has it) and when I change the water I make sure the water I put in his tank is very warm. I have towels that I put on and around the tank to keel heat in, but they aren't working well and I don't know what else I can do. Most advice I've found online is for power outages and would require me to be at home all day, but I have school keeping me away from home, and need to keep him warm(or at least warm enough) until friday evening.

 

Do you have a hot room in your house? In an emergency I moved my betta in My hot room and the tank stayed aT 76 with no heater. Can you raise your houses temp?? If you have it at 76 or higher the betta should be fine. If the tank has a lid then it could help keep the heat in the tank?

 

Can you keep the room warm?

 

Unless you're living in an igloo (i.e. so long as your place is a semi-reasonable temperature), the fish will probably be fine until Friday. In my opinion you'd probably do more harm than good trying to meddle with it.

 

Bud's tank is in the houses main area, so there isn't much I can do to heat the room, and I'm not strong enough to lift a 3.5 gallon tank without risking dropping it and doing more harm than good. He's on my desk, which is close to the kitchen, so whenever we cook he gets a bit of heat from that. I'll try warming the house a bit and keep any rooms with open windows closed. Thank you all for your advice and help. If you have any more let me know

 

I agree with Kgnao - for short term, stable temp is far more important than the correct temp, as long as it doesn't drop too low. I can't remember off the top of my head, but if the water gets below 68 f then you might need to worry. I do recommend towels or blankets around the tank though - without a heater to keep the temp stable, you want something outside to stable it. When adding water, keep it very close to the water in the tank - the change in temp is going to be more stressful than the cold, short term.

 

He will be fine.

 

u can use a led aquarium light 0r have a bottle of hot water in your tank that is short term will have to be done every day on the other hand if u want to cool down your tank use a bottle of water that has been frozen

 

I can't remember why I bought them, but I had some of those $1 window shield covers from Dollar Tree laying around. Since the wall is kinda cold at night I wrapped em around the tanks.

 

Good news! Bud has his new heater and it's working! He's much happier and more active, thank you all for the advice. It was very helpful for keeping him warm until he got his heater.