Posted: Sun Jul 10, 2016 11:50 am Re: minimum size debate: gallons vs. the formula
The water volume rule is in large part because of nitrate build up. You don't want too much nitrate in your water, so the more water you have to dilute the resulting nitrate, the better your turtle.
The measurements are for turtle comfort. The 1.5 times shell length is so your turtle can turn over--so it doesn't end up upside down under water without the space to right itself. The length is so it can at least do some swimming.
Personally, I'd say that minimum width should be much greater.
Tobi a RES born in 2012
1 dog, 1 teenager, 3 aquariums filled with fish, snails, shrimp and a bit of algae