I'm setting up two new tanks. Both will be getting filters that have long been in established tanks. The 20L will get an additional sponge filter from an established tank. Driftwood and plants from the existing tanks will also be added. I need to: #1. Transfer fish from a too-small tank to the new 5g. This one will get and older sponge filter. #2. Get my temperate river tank up and running. Petco has some long finned danios I'm coveting as they will fit the temperate range and should be hardy enough to deal with a semi-new tank. I don't know if I need to wait a few days, especially with the 5g, or can move them tomorrow or Monday. The last quick setup I did went well, but I really don't want to kill 3 more platties or a school of danios.