I don't recommend the tubs you get at Walmart meant for storage of clothes. I used one of these and it cracked and I put a tarp to hold water and not that great. https://www.walmart.com/ip/Sterilite-50-Gallon-Tote-Box-Titanium/15940602
I can't vouch for this, but I use a 40 gallon tub like this as part of the recirculator: http://www.cactushorsecor...llon-p/tskmt101.htm.
Key is it to be tough plastic. Something that can stand up to the sun and abuse.
I've also used these cement mixing tubs. A 20 gallon to sit the recirculator and catch tailings wich drains into a 10 gallon to place the pump to help stop from getting clogged. http://www.homedepot.com/...ic+black+cement+tubs
If you have a water source for your recirculator, you can be mobile, but with me, I need to bring at least 60 gallons of water here in AZ, so I am going nowhere quick. With my circulator, I can only set it up a short walk from the pick up.
My lessons learned about a recirculator in Central AZ:
A rule of thumb I like is the water should be at least twice as deep as the riffles or expanded metal. Seems you have a recirculating sluice or at least are using a pump for this.
Reason I bring it up is my first sluice I used the riffles that came with it and a 1000 GPH pump, which did not provide enough circulation for the sluice. The sluice was just too wide and the water flow did not even come above the riffles.
If you know the width of the sluice and the GPH or GPM rating of the pump, you may be able to get an educated guess. I was able to get my sluice to work with the 1000 GPH pump, but only with the 3/8" expanded metal or ribbed matting, otherwise I did not have enough water depth. When I got it dialed in, I could tell because the material would "dance" inside the expanded metal or in the ribbed matting.
Also, I found that with the expanded metal only or ribbed matting only, I really needed to classify. 1/2" classification was much to big and the rocks would not flow down, so I went down to 1/4 inch or 1/8 inch. When classifying that small, digging a single bucket and classifying would take up to an hour, so not very efficient. For my Area, when I classify to 1" I lose about 1/2 to 2/3 of the material to bigger than 1". As I classify smaller I lose half that material. So if I've dug 1 bucket of 1/8 material classified, I may have classified out up to 16 buckets, or about a half ton.
Also, for the wet recirculating, for every 5 gallons of material I ran, I had to muck out 1 gallon of mud. The dirt was so dry, I could also pout two to three gallons of water in each bucket. I had a 30 gallon reservoir to run this off of, and I would take at least 50 gallons of water out.