I sell wild discus; if you want anything else, go to Hans!
I sometimes have Discus Hans fish in stock, but not often (I may or may not have a tank at the BFD, haven't decided yet).
But, yea, you're right. You're going to hear from me on mixing discus from different sources.
Discus are some of the most susceptible fishes to disease problems, and when you mix fish from different sources, you're also mixing their loads of bacteria. You can take two tanks of discus that are 100% perfectly healthy, mix them, and have one batch die. That batch may or may not have even been the problem. The metaphor I've used before... The Spanish were perfectly healthy, the Mayans were perfectly healthy, you put them together, and the Mayans got sick and died (as well as some other reasons which are beyond the metaphor). As aquarists, we see this and think, "Oh, those Mayan discus are junk fish!", never realising that its the Spanish discus that were the problem -- and remain the problem every time other discus get added to the tank.
My advice on discus especially is to pick a source and stick with them. And to be very wary of imported discus, especially farm produced in Asia. Not only are those not necessarily the best sources to begin with, but they tend to send the junky fish over here (as do a lot of European sources).
Getting them from a good, reputable source -- like Hans -- is a big plus.
