Cycling - Water or Substrate?

So from various articles and reading around here, I've concluded that the tank water does not actually cycle and it is the substrate which is really needed to grow the necessary bacteria. Am I right to assume this?

The reason I'm bringing it up is because I'm currently transferring to a new tank and I've debating how much of the old tank water I should put into this tank. So far I've only added 5 gallons of old tank water and 65 gallons of fresh RO/DI water to the 90 gal tank. I personally feel the more gravel from my old tank I place in this tank, the quicker the cycle, or mini cycle will occur, but in order for the bacteria to spread to the new substrate does it not need a supply of ammonia/nitrite?

My old water does not contain either, but does have plenty of nitrates(20-25ppm). My other thought was, well I have tens of thousands of pods, and that sticking a piece of LR or 2 in the new tank now will surely kill off some pods and worms which should produce ammonia. If that's the case(if its enough), then the only reason I would even want to put any water from my old tank into this new tank is simply to get the nitrates at a more tolerable level for the fish. (I'm afraid of shocking them by bringing them to an environment with 0 nitrates from 20-25ppm.)

What are other people's perspective on this? Any links to a good article or book would be great too.

Thanks!

 

you are right that it is the substrate and rock that are colonized with bacteria, the water column will hold a small amount though.

you would need an ammonia source because different types of bacteria are responsible for each stage of the nitrogen cycle. the die off from the rock might not be enough, because it is basically cured live rock. Are you adding all live rock? Base rock?

 

The substrate and rock is where the majority of the bacteria will reside, unless you have bioballs or similar media. You need ammonia and nitrate for the bacteria to grow.

 

There's about 45 lbs of base rock in there now, and I have 40 lbs of LR waiting to be put in. I was debating putting in about 10-20 lbs tonight. A fly fell into the water last night, there's some ammonia right there I suppose I could put some flakes in the water as well to speed it up, I feel like a raw shrimp will be more than I need.

 

Maybe, but there is no such thing as over cycling. I prefer to be safe than sorry with these things, but i suppose if you stock slowly and test for ammonia and nitrites spikes regularly in the initial stages you should be fine either way.

 

Well I only have a Sailfin Blenny, 1 clownfish, a hermit crab, and a CuC to put into a 90 gallon tank at the moment. I feel like they will not create a lot of ammonia compared to the water volume, or enough ammonia which the current bacteria on the seeded gravel will be able to handle.

 

Yeah you should be good with those fish with that amount of cured LR. Once ammonia and nitrite are zero before you add them .

 

The amount of bacteria in the tank will adjust for the bio load you have. Then as you add more just go slow and let the bacteria build up for each new addition and you should be fine.