The copper on the disk (root control disc) for the Auto Pot System, is to stop root ingress in to the water holding tray!
The roots just don't like copper touching them.
You can also find copper coatings in RDWC systems & IWS flood and drain (Eb & Flow) systems.
Roots getting into areas such as drainage pipes and water inlet valves with Auto Pots, can cause all sorts of problems with blockages, with potential for flooding.
As for the "Pebbles/crocking" in pots, I saw this as be contentious and the last thing i wanted on a relaxing Saturday, was to be embroiled in an argument!
However it seems a majority of commenters, don't follow such a practise or advise it.
This make me feel more at ease, talking about it.
I supply some information that came to my notice some years ago and then I will add a little note at the end!
Are gardeners wrong to put 'crocks' in plant pots?
BBC Gardening
Published - 23 April 2014 (seven years ago to be exact)!
IMAGE SOURCE,ALAMY
For centuries, gardeners have put shards of pottery - "crocks" - at the bottom of plant pots to increase drainage. But a new study has debunked the tradition, writes Tom de Castella.
Crocks in pots are an article of faith for gardeners. A piece of crockery in the bottom of the pot aids drainage. It allows water to run off more quickly than soil would and prevents compost from clogging up the holes at the bottom of the pot. That at least is the age-old wisdom handed down from one generation of green-fingered sages to the next. Gardeners' Question Time, Monty Don and
Alan Titchmarsh have all endorsed the tradition.
But a study by consumer magazine Which? suggests it's a myth. Researchers planted 40 pots each with five "Million bells trailing yellow" - a flowering plant prone to root rot in saturated soils. Permutations involved plastic pot, and terracotta pot, and with either saucers or no saucers. Half got crocks, half did not. The plants were recorded for "vigour and flowering impact". The magazine found that the crocks "made no difference to how well our plants did".
You might think that the bigger gaps where soil meets bits of broken crockery would allow more water to filter through. But this turns out not to be the case, some argue. Guy Barter, chief horticultural adviser at the RHS, says a crock is actually likely to worsen drainage by creating a block. It's better to have a layer of sand underneath soil that will allow water to drain into it and later be sucked up by roots if needed. The only minor points in favour of crocks are that they might block drainage in hot weather, and also save money on compost. In most cases, people would be better off omitting them, he says.
Like many gardening "tips" it probably owes more to Victorian fashion than practicality, says Matthew Biggs, a panel member on Gardeners' Question Time. There was something comforting about re-used shards of terracotta performing magic inside the pot. "It's always sad when a tradition gets blown away by modern science." But many will probably ignore the science, and carry on with this "intuitive ritual" that is part of gardening heritage, he says.
I imagine the reason why "AutoPots" advise "Clay pebbles" is because the bottom of the pot is in constant contact with water.
It never dries up a water in a saucer will, just a though! Any Queries, contact AutoPot and ask them the question.
The lowest part of the substrate remain the dampest at the bottom of the pot as it is the area least exposed to evaporation.
All substrates have a, maximum water holding capacity, any more than the maximum and it will naturally drain away, due to a combination of gravity and being unable to hold more water than the maximum.
Deep rooted plants that seek out water, will easily hit the bottom of the pot.
Putting in pebbles raises the moistest part of the substrate, will mean less moisture holding substrate is available to supply the plant at the bottom of the pot.
Furthermore most substrates for cannabis focus on not only water holding capacity but also air holding capacity.
This means they are all relatively free draining, whilst still having a good water holding capacity.
It is better to add perlite to a soil mix to increase aeration pockets around the perlite granules,in order to increase oxygen to the roots.
As you water "Air" is drawn into the compost/substrate, the many tiny holes in the "Expanded" Perlite hold a great amount of air but also hold some water too!
Coco is a very fast drainer but it also holds a huge amount of water.
Yes I will admit in the past adding clay pebbles to my coco, as I was brought up on using "Crocking" in pots for the garden.
Then I read the latest info on it and stopped using as crocking instantly, with no ill effect.
However when I did use pebbles at the bottom of a pot, I still grew great cannabis.
Do or don't add pebbles, as long as you look after your plants needs, give them love and all the rest a plant needs to grow & you will do fine.