Originally Posted by Candee
I just added the water yesterday. Are u sure adding fish so soon is ok? Everyone has been telling me I have to let the water cycle for 2-3 weeks before adding fish.
Letting the water sit for 2-3 weeks or any length of time will do nothing to establish the cycle. This will take some explaining, so here goes. Planted tanks and non-planted tanks are biologically different, by which I mean that the biological processes acting on ammonia operate differently.
The nitrification cycle has to do with various types of nitrogen. There is ammonia, ammonium, nitrite and nitrate. Ammonia in acidic water (pH below 7) converts to ammonium which is basically harmless to fish and plants; ammonia is highly toxic to both fish and plants, and nitrite is slightly less toxic. Nitrate is basically harmless at normal (low) levels. Test kits mostly read ammonia/ammonium as ammonia; and ammonia detoxifiers (such as Prime water conditioner) do so by converting ammonia to ammonium.
In a non-planted tank, the ammonia produced by the fish and biological actions has to be "consumed" by nitrosomonas bacteria, and nitrite is produced as a result. Nitrosomonas bacteria consume both ammonia and ammonium, whichever is present. A second group of bacteria, called nitrospira [used to be thought to be nitrobacter] consume the nitrite and produce nitrate. This is called the nitrification cycle. A source of ammonia has to be added to the tank to start the cycle. Fish can do this, or non-fish cycling using pure ammonia, fish food, pieces of shrimp, etc. The nitrification cycle in any of these conditions takes from 2 to 8 weeks to establish itself, and this period is dependant upon a number of factors including water parameters (temp, pH, hardness). The various bacteria multiply in porportion to the available "food" they need, and when the tank is "cycled" it means that the level of nitrosomonas and nitrospira are adequate for the amount of ammonia dn nitrite that is available. The bacteria will increase if ammonia/nitrite increase (adding more fish, overfeeding, dead matter) and they will reduce (die off) if the ammonia/nitrite is reduced (removing fish, etc.). They remain in balance, and the tank is said to be biologically balanced with respect to the nitrification cycle.
In a planted tank, by which we mean a tank that is fairly heavily planted (not just a few plants), things work very differently. One of the nutrients plants must have is nitrogen. Scientific studies have proven that plants prefer nitrogen as ammonium, given the option. In acidic water, the ammonia produced by the fish is converted to ammonium and the plants grab it, almost all of it unless the tank is way out of balance. In basic (alkaline) water they take the ammonia and through the cell structure have a process that changes it to ammonium which they then use in photosynthesis. There is some evidence they can also use nitrite by converting it back to ammonium. And they use niotrate in the same way. However, the last process is certainly more involved for them, so their preference is to use ammonia/ammonium directly. They do this so well that the nitrification bacteria will be far less in a planted aquarium because there is not much ammonia or nitrite left after the plants grab it. The plants act as a sort of cycling by themselves, except they just take the ammonia and its gone.
So, in a planted tank, you can add fish on day one, and provided there are not many of them, the plants will grab the ammonia/ammonium and there is literally no establishment of a nitrification cycle, or to be more exact, it will establish itself but the fish will have no stress resulting from the cycling because the plants have consumed most of the ammonia. Planted tank authors have frequently written of this, and I have set up several planted tanks with fish the first day. In July I reset my 115g tank, put the plants and fish from the existing 90g in over two days (plants day one, 95 fish day two) and ammonia and nitrite were zero from day 1; nitrate was 5 and has remained at 5 ever since. There was no nitrification cycle to speak of, because the plants utilized the ammonia/ammonium from the start. Even with 95 fish, none were lost, and the only stress visible was the normal stress a fish goes through when it is netted out of a tank and into another. It is true that bacteria were probably on the wood and plant leaves I moved over. But years ago (1997/8) another experience is even more telling.
I was losing fish daily in my 115g tank, and those that were alive were extremely lethargic; the reason after weeks of testing and trying everything turned out to be a toxic substance leeching from two of the pieces of wood in the tank. I had to disinfect the entire tank to get rid of whatever it was. In one day, the fish were netted out into a spare 33g, the wood was discarded, the filter media was discarded, the plants were pulled out and washed as best as I could, the gravel was washed bucket by bucket in water as hot as I could stand, and the tank put back together and filled, and the fish added (about 90 of them), all within 12 hours. There could not have been one iota of bacteria, but not one fish died, ammonia and nitrite were zero. The plants did their job.
You can add a few fish, and gradually build the community. Use a good water conditioner before adding the fish (I always wait for the first fish to use conditioner, but doesn't matter as long as it's used).