Fully grown adults need huge tanks. I would say a footprint of 8x4 minimum.
They are big active and intelligent fish and anything smaller would be inhumane imo.
They eat food like crab,mussels, prawns and snails.Foods with a shell help keep their teeth ground down.
As beautiful as they are,I believe they are not a fish for the casual fish keeper.Its a fish that has always been on my wish list.
Due to the massive tank and filtration they require, unless I win the lottery I sadly will never have one.
They have definitely got appeal, but are a huge commitment if to be housed and cared for properly.