Hummidifier types and their additives

I've been running space heaters in my t room to keep the temp up during the cold snaps we've been having and was wondering on any knowledge about what kind of humidifier to use and if the additives that they sell to keep scale Algea and mildew down are safe for Ts.

I have a Holmes, model HM-1295, has a built in humidistat, isn't very accurate though. Uses a replaceable wick, cheap at Wally world, like $6. Haven't used it in a couple of years, when I did, filled it with distilled water only,
Keep the enclosure humidity by keeping water dishes full, light misting and moistening the substrate on species that may require it. Depending on the type of enclosure, cover some of the vent holes to adjust the humidity.
Just my thoughts.