I used to keep my softy in a tank without any sand. He was very active, swimming around, asking for food etc. Recently I put a sand layer (reading the tank layout suggestion for a softy). He is now hiding under the sand all the time day and night (only the edge of his nose is sticking out) without even asking for food. I don’t like it at all. Good old softy has gone away. Is it really necessary to keep the sand layer? Is this behavior going to change? Is this behavior strange? Please advise.