You can notice enough soil improvements by combining as little as 10% pumice with your garden soil mix. To enhance the porosity of plants such as succulents, apply 25% pumice mixed with 25% soil. You should also mix 25% compost and 25% large-grain soil. To improve soil drainage for plants that are susceptible to root rot such as euphorbia, mix 50% pumice with potting soil. Ideally, the general rule is to combine an equal amount of pumice with potting soil for potted succulents. For cacti plants, you can mix 60% pumice with 40% potting soil. You can also use pumice as a top dresser to mop up stagnant rainwater around plants.