Hi, your softshell turtle in reality is a chinese softshell turtle Pelodiscus sinensis, one of the most popular alongside the american species. And good that it is that species and not a spiny, otherwise it would be greatly undersized allongside its deformity. As for the deformity it migth or not be caused by a lack of calcium, Ive seen softys that were born just like that. It seems pretty healty asside from that. Make shure you give a varied diet including herbivorus fish pellets, predator pellets, worms, snails, grasshoppers, mosquito fish, etc. As for you tank it is a nice one, however I cant avoid but think that sand bank is occupying a woule lot of space. My sugestion would be for you to build a non mobile floating island made of cork for example, take out half the sand and spread the rest in the botom.
