My tanks are kept separate (2 SW, 1 FW, 1 QT), for the glass cleaners I leave them in the tank and each tank has it’s own. I share equipment between the tanks but always rinse everything in tap water after use, and for most then RO. I am not trying for hospital grade separation, just basic hygiene to avoid cross-contamination.
I am happy to move an animal from one tank to another however if everything is healthy - recently moved my sand sifting starfish from the small SW tank to the larger one as it had run out of food and was starving. Just picked it up from one tank, into a small container of SW from that tank, out of the SW and straight into the new tank. Obviously a risk but if I have no reason to think either tank is not healthy, a small one.