Most digital thermometers are worthless. They can give hobbyists a very generalized reading, but for the most part that reading isn’t going to be extremely accurate. Additionally, these thermometers can give completely insane readings and often break after only a few months of use. For these reasons, if you do plan on depending on thermometers, use multiple different styles from several different manufacturers. By using multiples (at least three), you can cross check their readings against each other and get a much better idea of what the actual temperature of your aquarium is.