Ya, where i am from we have a store that sells water troughs for cattle and horses. They are large and very sturdy.
THis is what I do on a smaller scale.
I have 2 30 gal
trashcans. 1 is for RO
water storage and 1 is for mixing and storing saltwater. I mix up about 25 gal
of salt water weekly and use it on my weekly water change procedure. I end up going thru about 20gal of RO
water every two weeks in evaporation replacment.
I imagen if you take this to the next level you could have a 200 gal
tub that you fill with RO
water and use to mix your saltwater with. Then when that is almost used up you could replentish the RO
water in it and start the mixing process over.