everyone is free to use whatever they want, of course. just be careful because aluminum foil reflects really well, maybe even too much, and that's the problem. if you position it correctly, you won't have any issues. but if you do like me and create a concave part, you risk having a spot where the light concentrates, and if it's on the plant, it will burn a leaf or worse. it happened to me with a plant that looked like a genetic defect. I removed the aluminum, and it went back to normal...