I should have clarified: by used material, i mean stuff that's still wet, like out of water for maybe an hour or two tops.
Good filters! I would take one of the trays from the new tank, and pour in a cup or two of gravel from the established tank. If not possible (sand or no substrate or w/e), then swap the sponges from the filters. Put the established sponges on the new tank, and the sponges from the new tank into the established filter. That will provide at least a little bio filtration for the new tank, while not impacting the established tank very much as every surface in that tank and other filter trays are already covered in bacteria.
Getting rid of some fish will make the ill-effects of the cycle less extreme. You have to remember though, the amount of fish you're using to cycle is how much that tank will learn to handle. As an example: you have x-size tank with 10 fish in it for 4-6 months. That tank is established for those fish. If you add another 20 fish to that tank, it will take another 2-4 weeks for the bacterial colony to increase enough to handle all the new fish. Going the other way, if you have 30 fish in an established tank and then remove 25 of them, a large quantity of bacteria will die off due to lack of food. If after you removed those 25 fish, wait a few months, then add 25 fish back, the tank will suffer the same re-colonization/re-cycle issues.
The best option here, in my opinion, would be if you could partition your SA tank to hold the africans, while letting the danios cycle the new tank. That depends on the temperature and ph requirements of your africans compared to your SA.
Even still, you will want to find some way to seed the bacterial colony in the new tank as this will speed up the cycle process and is much easier to do with an already established tank in the house. You will also want to monitor ammonia/nitrite every/every-other day and do frequent water changes to keep these values under control until you see your nitrate levels start to really climb.
