An international network of/for intelligent organisms
First of all, loose the agar, it's expensive, time consuming and a lot worse than paper as a main substrate. The only time you want agar is to make your maps and displays where clear agar looks a lot better than paper. Non nutrient water agar - that's important
Water - it just needs damp,.submerge Physarum and it'll start to fall apart
Ventilation you can pretty much ignore - opening a container to feed is enough, petri dishes I leave closed and wrapped in foil for days.
Distance - depends on the size of blob you add but a good 10cm or so
I'm updating it at the moment but there's a growth guide here -
Only when they look dry or when you add food ( assuming you'll be adding dry oats direct to the culture ). If I'm dotting oats out on a map they just a a single drop of water each.