We used a wash tub (the galvanized round ones) to set one up my daughters k-garden classroom. It holds one lilly, sonme duckweed and two big goldfish. If memory serves correctly the who setup was under 30 dollars.

Good luck
Angel

I called a company that supplies soap for Semi-Truck Washes, like a car wash but a lot bigger.
The soap comes in 55 gallon plastic barrels.
Once the threads start to strip out, they can't use them anymore, so they just give them away.

You could find a company like this, or even a carwash, that might give you one.

Just cut it in half, and use the bottom.

Cheap is good, but free is better.

That's a wonderful idea, I've a carwash about 1 mile away. I'll just give it a try.
Thanks. Agnès