Ya you should never keep 2 different species together, and really not with these kinds of frogs. I don't know a lot about PDF'S and I know a lot of them get there toxins from what they eat in wild but some may still carry some form of it without. Hopefully someone that knows more about them can confirm that for me if they see this. I know the part about what they eat in the wild is accurate just dont know if they carry any toxins naturally. Now the FBT's on the other hand do produce there own toxins and I really don't imagine the PDF's soaking in the same water is going to be good at all. And if the PDF's do have it in them naturally the 2 will mix in the water and then your going to have recipe for disaster for your frogs. But with that said you really shouldn't mix anyway, its really frowned upon.