I would guess whatever the recommended temperature is for the fish you want to put in? that way the proper bacteria develops? but I know nothing about what temperature does to fishless water. That would be my first guess though.
i doubt (but honestly dont know if) keeping your tank at 86 degrees will make it cycle faster.
BUT if the fish you would like to keep in your tank prefer 78 deg, then use this type to adjust the the heater settings and cycle the tank at 'their' proper temp.
actually, you should have the tank at about 84 for cycling. the higher temp is better for bacteria growth. read up on the all the cycling stickies we have posted on the site, and they should answer any questions you may have.
