Making a miniature reedbed to gain knowledge with grey water treatment

I have always liked to make miniature versions of what normally would be a bigger project, in order to gain experience and knowledge due to the restraints of living in a small apartment. I have done several things in this manner, such as composting, making papercrete bricks, biogas, etc. I know the basics of how reedbeds work but I was wondering if it's plausble to make a light-weight, small and functional reedbed using say, a 40 liter glass fish tank? I was thinking that I could cover up all the sides to protect the roots from light but I can keep a removable side to see everything in action. From what I read, I can use common reed (perhaps I can include other riparian plants as well) since they break down organic matter and absorb excess nutrients from grey water. This is a really simple diagram based on one of Geoff Lawton's videos on making a reedbed of what I would like to do:



The way it works (in theory) is simple, grey water with small organic particles goes into the perforated tube on the left, once its like at 3/4 of it's capacity I let it sit for a while to let the plants process all that grey water. I cover the tube with a cap to avoid any fetid smell. So thus, my questions are the following:

Besides gravel and sand, can you use other lighter materials such as perlite so that it can be moved around or possibly made portable for demonstrations?
I know I have to let the grey water sit for a bit before it cleans it up but how long do you think is sufficient? days, weeks?
When do you think the reedbed will need maintenance? does that involve just pruning or uprooting the plants or does it mean taking everything out, cleaning it and/or replacing the substrate?

Thank you for your help!

Mike Autumn wrote:....since they break down organic matter and absorb excess nutrients from grey water. ...


...does that involve just pruning or uprooting the plants or does it mean taking everything out, cleaning it and/or replacing the substrate?!

Not quite. There is another step. The reefs have a hollow stem. This allows the plant to pull air down and release it from the roots which oxygenates the grew water. Aerobic bacteria can now begin the process of breaking down the nutrients which are then absorbed by the reed for growth. Thus the nutrients are pulled from the water and converted into plant matter.

Once the reed has reached full maturity and stopped growing its intake of nutrients slows down. At this point you want to Harvest the plant to produce mulch or compost and allow the pruned plant to continue growing.

Hope this helps