i am switching tanks from 20 to 45 is there a liquid i can buy to instantly get the

[Cliff]

Then there's the fact that completely new water will start a mini-cycle all over again, more stress. Or, is the OP gonna keep both running and do a 'Fishless-Cycle'? By using some of the water from the 20, all the Bacteria that eat Nitrites won't die off( The old water containing some), while the new water cycles and the other BB that eat Ammonia start to colonize. This would make the mini-cycle smaller and shorter in duration. Not to mention that, all the beneficial Bacteria in the Sponge and filter would starve to death before Nitrites appear in totally new water.

That is just not the case. Practically all bacteria that we need to keep the water safe for our fish is in the filter media, not the water. What feeds the bacteria is the waste that the fish produces, not eleiments in the water. I have completely replaced the tank water when moving tanks or upgrading tanks (just like the op) many times without even the smallest spike what so ever. The fish will actually benifit from lots of fresh clean water

Edit: I should have just typed "+1 to 850R" and saved myself from typing the above

[KingFisher]

+1 to 850 and Cliff.

[Honey Badger 1]

Then there's the fact that completely new water will start a mini-cycle all over again, more stress.

Lol

Water doesn't cycle.

Exactly.
+2 to 850r, Cliff, and Kingfisher.