But where, oh where, do they come from?

im gonna take a swing at this -since bacteria needs nourishment to sustain itself, like us, im guessing they stay around their original food source; pooh, and the substrate the pooh rests on. so to make it into the aquarium, they may live naturally in the animals' digestive tracks...
but that wouldnt explain how ammonia bottles can cycle a tank...hmmm

Poo is not the primary food source for nitrification bacteria, it is the food source for saprophytic and heterotrophic bacteria. Those heterotrophic bacteria do themselves release ammonia. Most ammonia in a fish-only tank comes from the fish's gills directly released from the fish's blood stream across the gills into the water.

Bacteria come from other bacteria of their own kind. Some have spore forms which can be transmitted through the air. FW nitrification bacteria don't form spores, so they have to come from others of their own kind directly, without a resting or dormant phase. That is why using filter media from a mature tank is the fastest way to establish the nitrification bacteria in a new tank. If not available, the rock wool from "potted" plants freshly recieved at the LFS are the next best souce of these bacteria.

it could come from the tapwater, new fish/plants, anything that isn't sterile!

That is precisely why there are products such as Bio-Spira, and techniques such as Dr Chris Cow's original series on fishless cycling. The bacteria which establish in FW tanks are fragile, but they are not rare. The trick is to get them into your tank and get them established without hurting your fish.

pophead said:

it could come from the tapwater, new fish/plants, anything that isn't sterile!

Click to expand...

I think it's an interesting question. The bacteria will grow in water without seeding, provided a source of food (ammonia) is present, but will take a long time to become well established. It makes sense, to me, that a small amount is present in the water to begin with...but can it come from the tapwater, especially if it's chlorinated/chloraminated?

Slappy*McFish said:

That's the way I do it...overnight cycling...add fish the next day.

Click to expand...

haha me too, but i throw the fish in as soon as the filter is running, but its usually a light load at first

Fishless cycling of an aquarium without any intentional seeding does work. So the bacteria must come from the water, the air, or something you put in the water (like your hands or a filter tube).

I'm guessing it's not the water, if you start with chlorinated water. I don't know if nitrifying bacteria can stand those levels of chlorine, but I doubt it. That leaves the air, or something else you stick in the tank. Here's a quote from the Skeptical Aquarist:

"Nitrifying bacteria are so apt to scavenge any source of nitrogen — whether in the form of ammonia or as nitrite — that it takes some pretty good lab technique to keep suitable cultures free of them.... A lab technician could tell you better than I, how nitrifying bacteria creep in and "contaminate" many delicate experiments. A whole chapter narrating some adventures with the disconcerting results of these bacterial "ghosts and wraiths" features in John Postgate's The Outer Reaches of Life, available in paperback at www.amazon.com. This book is too good to miss!"
(from http://www.skepticalaquarist.com/docs/startover/fishless.shtml)

I haven't read the book he mentions, but he makes it sound like these bacteria are pretty much everywhere. Perhaps they do float in through the air -- not in spore form, I would guess on particles of dust, debris, or organic material -- or perhaps they ride in on our skin.

-ariston
:dive: