Only African Tigerfish (Subfamily Hydrocyninae) and South American Trahiras or Tigerfish (Family Erythrinidae) are illegal in Florida. When I last checked with FWC Datnoids were legal.
Only Silver Arowanas are the only Boney tongue fish allowed in Florida. If I am not mistaken the blue Arowana is the Juvinile version of the Black Arowanna, which are illegal. When you get a Liscense to sell tropical fish in the State of Florida it comes with the restricted/prohibited list printed on it. ALL LFS in the state of Florida must have that liscense to sell fish.
That may be the case. I have never heard of the loop hole. I have heard of the fines though LOL. FWC Clearly states Any Boney tongue fish EXCEPT Silver Arowana is illegal. Last time I checked An Arowana is considered a boney tongue fish whether you call it Silver, Black or Blue. Anything is possible I guess. I see alot of Blue/Black sold down south.