You know, I was wondering that very thing, about mixing Asian and German fish. So I asked Stendker in Germany. Here's their reply:
Dear Don,
many thanks for your kind email and your inquiry!
The colour strains you are asking for are typical for Asian discus. We
do not intend to breed white or yellow discus in the future. We would
have to breed with discus fish from Asia and this is a much too high
risk for all discus fish in our hatchery!
Please keep in mind that you should not mix discus fish from different
breeders. We understood that you already have some Stendker discus fish,
so if you are keen on these new strains from Kenny we recommend you to
work with a complete new tank and separate filters, nets, .... so that
all fish stay healthy!
Kind regards,
Sandra & Bastian
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Diskuszucht Stendker GmbH & CoKG
Am Holzbach 18
48231 Warendorf
Tel. 02581 60627
Fax 02581 633205
www.diskuszucht-stendker.de