We all have seen the great Water storage IBC Totes that many of us use. Here are a few hints on how to find them.
I use this search page to search Craigs list. There are a few others sites to search Carigs list also.
Search for water tote. it seems to find them. Also search for storage tank. Lots of junk in this search.
They seem to range from $40 to $100.
Make sure that they weren't used for anything that could kill you fish. Food grade.
Clean them out good.
They have a great drain fitting - not always large enough.
LEAVE them in the frame - Folks have had them collapse when taken out.
There are lots of ways to use them. Michelle silva has four of them in a cascading overflow set up that looks great. Many folks cut the top frame section off and use it for gravel beds. Lots examples on youtube and here.
Uniseals work great on them.
They Do get GREEN algae water when they are exposed to sunlight.
Tell us all how you got yours and if you can give us leads to find them cheap and local.
Maybe there are local sources of them that are industrial. As always be prepared to haul them in a trailer when ever possible. they are big.