Perlite is really light and fragile and it floats and depending on the size of it you might really cures yourself if you let it into your system.
I wouldn't personally use it in a normal gravel bed situation.
Maybe perhaps in a hanging basket with dribble irrigation provided you are not worried about it affecting the fish's gills.
I use good old heavy gravel.
Well I imagine that after your first couple harvesting of root-balls and re-planting, the perlite and gravel will just be pretty mixed together. I don't know if you've ever worked with perlite before...but it does seem to tend to break down, especially when exposed to excess air and lights. Keeping it in the bottom 10" long term might be tough without some sort of barrier screen. But I imagine such a screen would become a clogged up anaerobic mess right quick...
Besides, perlite unlike gravel, hydroton, lava rock etc...has no cation exchange capacity as far as I know...which probably doesn't mean squat in a hydro system proper, but certainly might in the low (relatively speaking) nutrient concentration environment of an AP system. (Though this fact probably isn't the deal breaker, but still...)
Jeremy K said:
How about perlite for about the first 10" or bottom 10" and cover it with lava or pea gravel?
I ran out of perlite a few months ago. I'm as surprised as you are.
I've used both perlite and vermiculite/ gravel/hydroton layers. Other than worrying about my fish health I have had reasonably good luck with both. I am going to go with expanded shale shortly. Light and reasonably priced with great surface are.
Check this out. I have a video showing a basic intro to my system. It shows my perlite beds. I use it as a wicking media.
Can I find that on your page, or is there a link I should follow?