I am creating a large indoor garden in a space with concrete floors. I would like to use galvanized horse/livestock water troughs for raised beds. I will need to drill holes in the bottom for drainage, but I'm stumped on what to put underneath to catch water as it drains out through the soil.
I will probably elevate the tanks on bricks or concrete blocks, but don't want to do permanent damage to the concrete floor if the tanks drain on them over a period of years.
What I need is a huge "tray" of some type to catch water that drains out. Does anyone have a clue where I could look for something like that?