Talking with my LFS about a phosphate issue I’ve been having. One thing he asked is how old is the sand bed, mine is at least 11 years old, he told me I need to remove and put new sand in. Is this true, I always thought never mess with the sand bed, now he did say to do it increments like 1/4 at a time until it’s all out then add new sand, he said this shound be done every 5-7 years, if that’s the case I’m at least at 11 from when I have owned the current sand, but it’s older than that because I bought the whole set up from someone and I don’t know how long they had the same sand before I got it, I know I have had the current sand for 11 years. Thanks and if what he said is true that it’s time to change it do I really need to do it in increments or can I do it all at once?