what i use, since i work at pizza hut we have alot of soda crates. the blue creats that 2 liter bottles and 20 ounce bottles come in. i have about 8 of those and i place them across the bottom for run off!! they also make good high adjustments for younger plants coming into older grow so you dont have to lower the lights
go behind a pizza hut in your area and see if they have any of the plastic crates i speek of. pepsi and coca cola leave them there. not encouraging stealing but lets just say they have alot of them!