Mixing Discus from different sources is risky, but what about tank mates?

Hi, I‘m new to all this, never kept discus before, first ever post... may i ask you would I be risking the health of my new discus if adding tank mates (rummy nose tetras) from an older established community aquarium in to a newly cycled tank before adding discus? The idea being that I could introduce a natural bioload in the form of rummy noses and maintain the cycle before adding a group of discus. My concern is that I live in Uk and want to get German Stendker‘s. My rummy noses are likely from an Asian source and I’m am unsure if there is a chance of cross contamination from other fish knowing the risk of keeping discus from different sources together? All hypothetical, just doing ongoing research in preparation, and haven’t come across an answer to the this type of question so far online. hope this makes sense. Thanks.

if they are healthy , you should not have any problem .

Ok, thank you. But...... if the rummy noses are in a community aquarium with angelfish, is their a possibility of worms being an issue, as far as I’m aware they (Or any other tank members) have never been symptomatic but I’ve never wormed either.
Thoughts?

I wouldn't. Not if the rummy nose are not domestically bred, for sure. Set them up in a separate QT tank and treat them the same way you QT Discus, hero fish and all. Not what you wanted to here. Sorry...

Ok so, QT and treat the rummy’s despite the fact there is no apparent health problem and they have been living happily in a community for some time. I’m still not really clear. Lots of people manage Discus with tetras and others etc. So what’s the safest way to add add companion fish? Who goes in first and what QT methods should I be using? Sorry for all the questions I just wouldn’t want to get it wrong for the sake of housing my current fish when I could just reduce the risk completely and go Discus only. I do appreciate any feedback of course so please feel free not to sugar coat.

What I would do in your case is keep both Discus and tank mates is separate tanks for 3 weeks. Don't share any equipment or if you do, sterilize with bleach between tanks. If nothing is wrong with either group for 3 weeks, take your least quality Discus and put it in with the tank mates for a week to 10 days. (full budgets would tell you to wait longer and I guess they're right) If the Discus remains healthy in that amount of time I'd consider it safe to mix the 2 groups.