Unclefrancy please help me . Sorry if I am assuming it's a round tub since you gave diameter ! You said 22" diameter x 13" high? Are each of the four all in a separate 22" tub ? One 22"x13" round can only hold at best 23 gallons ! http://www.gardenponds.com/Round-Pond-Calculator.html
Is it radius not diameter ?
Maybe it's my old screen seeing 22 inches diameter and may / could be 22 feet diameter instead? Sorry if I'm just seeing this wrong. 22 feet x 13 inches would be 2850 gallons and that's great ! Wish I could have that.
Did you get them as adults and or raise them from babies? Could you help me understand the tubs / size better , thanks' !