Typically, if you’re experiencing fungus on your succulent soil, you have a humidity problem. Either the air around your succulents is too humid, or the soil is too wet.
Sometimes having a lid over your succulent seeds creates too much humidity. If this is the case for you, be sure to lift the lid daily to let air circulate through. You can also prop it up just a little so that air can get through.
If you don’t have a lid on your seeds and you’re still getting fungus, your soil is staying too wet. It’s either not well-draining, or you are watering too often and not letting the soil dry out in between.
Allow for more air circulation, and be sure your soil drains after watering, and you should be well on your way for succulent success!