Perlite Layer After 4 Years in the Bottom of a Wicking Bed

Four years ago I built some flow though wicking beds where I used a layer of perlite to separate the soil from the lava rock and pipe false bottom. Many were concerned the layer would not hold up. Well now I am taking the beds apart to change their configuration. Good chance to take a look inside and see how well the perlite was able to maintain its stratification layer.