I was wondering. In the reptile world, we use plastic tubs for all sorts of reptiles and amphibians. I've been doing a little digging and all the information I have found has said it is safe to use Rubbermaid or Sterilite tubs as "tanks" for fish.
While they may not be pleasing to the eye, they would serve the purpose of holding water and providing space for the animal to live. They are lightweight when empty as opposed to glass aquariums. Rubbermaid makes some large tubs, some stock tanks go up to 300g. But the kind you can buy in Walmart or Target is what I'm looking at to use.
For example, I have a Rubbermaid tub here that holds 10+ gallons of water (have not filled it all the way yet, so I'll know how much it holds when I'm done). A HOB filter fits perfectly onto the rim of the tub and a heater could easily be installed as well. A downfall to the use of a tub is lighting. Finding a cover or light fixture to fit over top the tub is harder than with a glass aquarium.
So are these tubs usable as aquariums, given that we don't care about how it looks? (especially in breeding set ups.