I hope for the sake of the frogs that that is not the case. One of main reasons the 'old geezers' frown on mixing is because they want to see the lines of frogs currently in the hobby well represented long into the future. This means as true to their natural counterparts as possible. Since you indicated you've had breeding 'success' in mixed tanks, I would be willing to bet that you have produced some hybrid darts. Have you sold or given away any offspring from your mixed tanks?