Instant cycle?

[Joshuakahan]

Using water from your established tank achieves little to nothing in regard to BB transfer. Using 50% of your substrate from your established tank, as well as a filter, will put you on the right track, especially if the new arrival is small. In the meantime, adding your other temporary occupant, just to give you an ammonia source, is also a good shout.

However, my concern is not for your new tank, but for your already established tank, the one where you've took 50% of the substrate out, as well as a filter. That is a lot of BB you've transferred and if you've got fish in that established tank you need to keep your eye on your parameters and/or monitor your fish for unusual behaviour.

My donor tank is a 120 with a fluval 306, 2 AC70s, 1 AC 50 and two bio wheel 350, so I moved the AC50 to the 40. I also only took about 10% of the substrate from the 120. I do 50% WC twice a week. So I think my 120 should still be fine or do you think I’m wrong on that?

 

[Joshuakahan]

Like esoxlucius said, using old tank water will do little/nothing for you. That gravel and filter, provided they were in service in a long established and healthy tank is all you need to be up and running in a new tank.

All I do is swap an old, well established filter onto a brand new setup and I'm off and running, producing nothing but nitrates.

The gravel is about 3 years old and the AC50 I moved is about 1 year old, all from a heavily stocked tank

 

[Rocksor]

The gravel is about 3 years old and the AC50 I moved is about 1 year old, all from a heavily stocked tank

Just remember that bacteria do not evenly distribute themselves across all filters. So there is a chance that a single filter houses 80% of you BB in your old tank, and the other filters may have a very small amount of BB or none, just as an example.

I have no doubt the gravel will have the organic compound consuming bacteria since most a lot of detritus makes its way into the substrate.

 

[Zanzag]

can also use stem plants in addition to what you are already doing . something fast growing will help soak up organic waste