A few photos of the setup:
20 litre oil drum, grabbed from a skip behind a car servicing centre. Hose and fittings bought new, can be a bit pricey, but Western Australia's a bit ridiculous price wise since they got rid of their manufacturing base.
Luckily the windows at my mum's place are pretty badly fitted, so there was a gap big enough to get the hoses through.
Just above is the car port, so the bank is shaded throughout the day. This seems to be important.
The very ghetto air pump housing. Taken from a old vacuum cleaner, stuck in some tupperware. Worked fairly well minus the fact that whatever plastic that is just does not want to adhere to any kind of glue, at all. Hence the tape and string, and it still leaked a bit.
Close enough is good enough.