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Okay, just water isn't going to make much of a difference some way really give you much of a kickstart. There will be a little bit of bacteria are not really anything to write home about. What you need is media out of the filtration system. If you have got a tank that is cycled at the moment, I would suggest that you open up the filtration and see what sort of media is inside. It really depends what sort of media you have got. It is just sponge, you could take a small piece and implant in the new filtration as well as squeezing out all the water from the sponge with any bits of gun that may be on the outside. If the filter consists on ceramic media, like little balls, you could take a few of them and put them in the new filter. This is by far the best way of kickstarting the biological filter.
You can also use products such as stress zyme, stability or prime. These products will certainly help protect the fish whilst the tank is cycling, they do contain a certain type of bacteria that will help cycle your tank.
