I live in Costa Rica and we have a real problem with mold growing on the inside of lenses etc. I bought a 200-500mm
zoom, and even though I keep it in a well ventilated room, mold developed within 6 months. I did learn keeping the lenses in a lens bag or closed camera bag is a bad idea and it's important to let air circulate as freely as possible around everything, but you just can't stop it from happening. I managed to get the front element off my 80-200 zoom and clean the glass, but can't figure out how to get open the 200-500. Any suggestions would be appreciated.