CactiGuide.com

I am using a heating pad with a thermostat to sow cacti seeds.
I have read that some say to leave the mat on 24/7.
Should i run the heating mats continuously or is it better to run it set to a certain temperature? If you run it at a certain temperature, what is the ideal temperature to sow seeds?

What kind of species are you planning on growing? Different species prefer different germination temps.

I am growing a variety of cacti and succulent seeds. Most of them are cactus such as MAMMILLARIA, thelocactus, ariocarpus, trichocereus, and some mixed cacti seeds. The succulents are mostly the caudiciforms.

I only have 1 year experience with sowing. I used the guidelines from Succulenta (Dutch-Belgian Cactus Society). They suggest 20-24°C. They also write —if you are sowing many different species— the first 7-10 days 20°C, then 25°C for 7-10 days, then 30°C for 7-10 days and finally 25°C for the remainder of the time. I also heard a 10°C difference between day and night temperature is advisable. Which in some cases is harder to obtain. I have 2 propagation boxes with heat mats and additional lights. The heat mats have an external sensor to measure the temperature. It is always a bit hotter than the set temperature, especially when there is no fresh air supply in the initial germination phase. Once they germinate, I find care a bit more difficult.

I don't know the ideal temperature. I have 2 heat mats but they don't have thermostats. I use grow lights on timers and have the grow lights and heat mats both on the same timer so the heat goes off at night to mimic night and day temperature swings.
I also only have one year experience but it has worked well so far.

Leave it on 24/7. They hardly draw any power and you’ll still get the day/night temperature change

I have cheap Amazon heat mats,and not so cheap grow lights but the mats don't have thermostats,so I don't know about temps. But I put the mats to come on the same time as the lights do on a timer. That helps imitate day and night. Is it necessary? I don't know but it seems to work for me,and trying to imitate mother nature sounds like a good idea. And I read a lot of folks do it that way. I'm on my 2nd year starting seed,and I don't see any reason to run the mats at night.
I would think you could set your thermostat pretty high. Because ground in the summer sun can get pretty warm. I doubt any grow mat would go high enough to roast a cactus. But you didn't mention what range the thermostat goes to?

It also depends on the power of the mat (like ~7 W) and size of the incubator, is the later open or closed, well insulated and so on. In some cases it would just slightly increase the temperature or in others may reach 10 C up. Try it first how it works in your setup. Then leave it on till the seeds germinate or till the end of winter. This also depends on your room temps.