I don't know if perlite and vermiculite absorb water or not, I think they do and that's good but doesn't cut down on weight, if that's the goal.

I would think that styrofoam bits would not soak up water and mix in well, and it's a way to repurpose otherwise difficult to recycle waste.

Or maybe packing peanuts (the wheat-based kind.) I'd also add some of that water-retention gel to the soil mix. It will expand the soil some while holding onto the water you pour in.

Used to be that I got them all the time when I got packages, but they are getting hard to come by. I still have a bag of them but when it is gone, I don't know what I will do.

The one problem you might have with a hanging pot is that they dry out so quickly, and if you don't have enough soil, they may not do well. I have never tried packing peanuts in hanging baskets and I still have trouble with drying out.

is to put a few empty plastic water bottles in the bottom and fill up the rest of the pot with whatever potting soil you are using. There would be enough space around and above the bottles for enough soil for the plants. You would have to be sure to water often, though.

Or packing peanuts covered with ground cloth or some news papers. The soda or beer cans work cuz I've done it. I've had a penchant for old galvanized wash tubs and buckets in these last few years. They make great homes for my succulents. Gone crazy for chicks and hens.

those hens and chicks will reproduce a trail all the way down to my house.

I love how they spread and that you can basically start them by just setting them in the soil. I'm nuts for sedum for the same reason. Plus I've discovered ice plants. Woo Hoo!

Ours died last year but we found more to get it established again. We do a lot of sedums because they are so drought tolerant.

I'd like to zeroscape as much as possible.

We have a vegetable garden and that requires a good bit of water. We have barrels at the front and back gutters so we collect most of what we need if we don't water flowers. We have a few annuals around the house for all summer color, but mostly we have drought tolerant plants. And NO grass except the bermuda that sneaks in.

Good luck with your zeroscape. Post pix when you can.

I'll post pictures doon. I'm away from home right now. But doon.