We haven't updated in a while as they really haven't had much of a change other than there size lately. The largest is now about 3 inches and little one is only 1.5 inches, so there is quite a size difference. Since we will have to eventually create a terrarium for the critters we decided to upgrade to a 10 gallon tank today, but only put about 3.5 gallons of water in it. This gives them plenty of space to swim around and grow but will not become overwhelming to change the water. It should also be ample space so that the littlest will not get eaten or taken over by the larger.