By moving soil/substrate over you run the risk of moving any pathogens or parasites into the new tank as well. Would be better to purchase a new culture. Also worth thinking about taking part of that new culture and using it to set up some breeding colonies (put some blocks of fine charcoal in a container with half an inch of water, feed with some yeast or springtails food and they will breed) so that you have a ready supply in the future

 

Simon has got the nail on the head. Transferring ANYTHING between tanks could transfer pathogens or parasites

I would recommend getting new cultures of Isopods and springtails and keeping them cultures outside of any tanks and then seed the tanks with parts of the master culture so that you always have a supply of Isopods and springtails.

 

Transferring ANYTHING between tanks could transfer pathogens or parasites

How about frogs move?

 

Thanks everyone. Super helpful. It seems like the sources I used before to order springtails and isopods seem to be out of stock at the moment. Where are people getting them? If it's ok to recommend sources here.

 

There are listings in the Marketplace that a person could check into. Spings and isopods are items that providers tend to have pretty consistently, so someone who has posted them for sale in the recent past is likely to still have some available.

Or you could post a wanted ad there, but I think PMing existing sellers would be more productive in this situation.