Help - steeling media from another tank (long)

[KLKelly]

Hi Guys - I have an opportunity to get fish I've been looking for for months tomorrow.  They are about 1" each. I plan on getting 10 or 12.

I plan on putting them in a used 10G and just bought a new AC20 this morning for it.

* I have a cycled 10 gallon with only 7 smaller fish in it.  I want to steel enough media from it so I can instantly cycle the new 10 gallon but I don't want the existing 10 gallon to crash.

* In the cycled 10G tank (set up for three months) so far.  Here's what I have in it right now:
Barebottom
AC 20 - with a filter foam, 1/2 cup new bioballs put in last week, carbon, and a 1/2cup of older bioballs hanging from fishing line outside the filter in the filter outflow.
3 potted plants that hit the top of the water - 2 spiral vals and a bacopa caroliniana.
2 nylons of gravel containing 1/2 c of gravel each on the tank floor.
Drift wood.
4 3/4Inch threadfin rainbows.
3 3/4Inch Signifer rainbows
Ammonia is zero in this tank and Nitrates also consistently showing up as zero.

What media can I steel from this tank that would have the best odds of instantly cycling the used 10gallon but not cause a harmful blip in the existing tank?  As you can tell I'm nervous about it and I'm sure you guys have done this type of thing lots

Thanks!

Karrie

[RoxyDog]

I would think you'd be fine just stealing the 1/2 cup of older bioballs...?

[darkdep]

Agreed.  In an established tank the bacteria literally cover everything; but the concentration is highest in the biomedia.  There isn't usually enough on the substrate or decorations to cycle a new tank instantly (although it helps).  I have done this many times (I hate cycling new tanks from scratch) and I usually take half the biomedia from a running AC to use in a new AC and everything has always worked out perfectly.  I would also suggest the older bioballs go to the new tank.

[KLKelly]

Thanks guys.  Going to set it up now.

Karrie

[pegasus]

But here's the problem:
Bio micro culture of a tank is directly proportionate to the biomass of the occupants and the waste they produce. So your cycled tank as 6" of fish while you would be introducing 12" of new fish to a new tank.
Best bet is to do as proposed above by others, also split the water (75% to the new tank) and move the present fish into the new tank.

[Woody]

Pegasus is right, you are going to have to watch the sudden increase in bio-load, but I do this quite often, steal media and water from one tank to start another. Over the next month just be easy on the feedings and I perform large water changes 30  to 40% every 2 or 3 days, with dechlorinated water until the bacteria increases in sufficient numbers to handle the increased bio-load.
Personally I also throw in a large handful of java moss, I find this helps.

Woody

[pegasus]

Now Woody is right, java moss is a much better substrate to bacteria than plain glass or slate. I've seen myself manytimes installing a new filter to a new tank by just rinsing/cleaning a dirty sponge in it and leaving it there floating for a few days.