As long as they make up a small part of the soil and have plenty of drainage-enhancing ingredients mixed in, peat moss and coco coir are safe to use with aloe vera. Both peat moss and coco coir have water-retaining capability, which some growers feel is unsafe for a desert plant like aloe. The concern is that the soil will stay damp for too long, thus increasing the chances for root rot. If you're planting in soil that's primarily peat or coco coir, that could definitely happen. But the addition of sand, perlite or pumice adds the necessary drainage element, making peat and coco coir a safe choice when used correctly.