These new fish should go in mature systems. We currently have four (three in the tent, one in the bank). Michel said 100 max per system, at this stage. So if we throw out all the wild fish and sell / give away the goldfish, we could spread them out, for now. But we have to start building quickly, because we need established bacteria before increasing fish density.
I'm starting to doubt whether I can make it before christmas with these african ones. The construction with my dad bringing us to Amsterdam might not work because it's on sunday. We'll call the farmer tomorrow and we'll know more.