can ammonia be too high in a fishless cycle?

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europas_ice

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When starting a fishless cycle, would too high an ammonia concentration have any negative effects on getting the cycle going?
 
If it is too high the bacteria will not grow because the ammonia levels will inhibit their growth as well. I would try to stay below 5ppm (4ppm is better)any more the that and your nitrite phase could go on forever. (or at least seem like it)
 
Thanks for your reply. I'm at about 8 ppm now. I will do a pwc and that should bring me down to around 4.
 
8ppm is a bit high. How long have you been cycing for? If you are starting to see nitrIte, I would hold off on the water change. If you just started the cycle and overdosed, I would do a 50% water change (this will get you close to 4ppm depending on the accuracy of your test method).

While most of the bacteria is attached to the filter media, glass, and substrate of the tank, there is always some bacteria that is in the water itself, and this is the bacteria that will float around and attach to new areas.
 
In the later stages of the cycle, when nitrites appear, don't exceed 3ppm of ammonia, or you can stall the cycle. Too much ammonia will kill the bacteria that break down nitrite into nitrate.

3ppm would be lethal to fish, so there's no reason your tank should ever get that high, so maintaining 3ppm during cycling means you'll have more than enough bacteria to handle a normal fishload when the cycle completes.
 
To add to what malkore said,

I follow the make WAYYY more bacteria than your full fishload will need philosophy. That is make sure the bacteria in your fishless cycle can consume 2.5-3ppm in under 24hours. If you can get close to this point you can add all of your fish to the tank at the same time without fear of causing a cycle. I actually think its LESS stressful to do it this way then adding in a couple fish at a time since you may run into territory issues if you stock a couple at a time (the early fish might be aggressive to later fish). Also if you do a fishless cycle and then only add a couple of fish a lot of the beneficial bacteria you have built up will die because there isn't enough food to go around. By having more bacteria than your tank will need you can safely avoid possible minicycles when adding fish.

If you do add fish in slowly the general recommendation is to add the behaviorally timid ones first (say cherry barbs or tetras), and then the more aggressive ones later (tiger barbs, gouramis, etc).

But this is just my opinion.
 
The optimal dose of ammonia for fishless cycle has not been scientifically studied, that I know of. Since many have chosen an ammonia level of 5 ppm and had success, it has become more of a tradition than established fact. It is presumed that there is a level at which bacteria will multiply the fastest, below which they will multiply slower and above which they multiply slower. What that level's value is, is just a guess. Low levels, even below the kits detection limit of 0.25 ppm will establish a bacterial colony, it takes about 7 weeks at 78 degrees, pH of 7.6. (I know this, because I have done it twice). There is a hope that a level of 2ppm would be faster, and a level of 5 ppm would be faster yet, but a fear that a level above 5ppm would be slower.

Regardless, once you start to see nitrite levels, it is safe to assume that you have a good start to your nitrosomas colony, and they will no longer need high levels of ammonia to continue to grow. I would add no more ammonia until the level goes to zero, then administer 0.5 to 1 ppm per day thereafter. I suggest this because if you maintain a high ammonia level, all of that ammonia will end up converted to nitrite, and the nitrobacter bacteria are slower growing than the nitrosomas. Thus, to continue to pump high levels of ammonia into the tank will create a large nitrite hump that will take longer for the nitrobacter to catch up with.

Somehow the mathemetician in me feels that the optimal (fastest) bio-filter growth recipe would be an initially high level of ammonia (1 to 5 ppm) followed by smaller ammonia doses (0.25 to 1ppm per day) once the ammonia has gone to zero. I have actually set up identical tanks to test this "dose response" theory, but somehow life always gets in the way and makes me stop the experiment before it is finished. This is truly an area where the home aquarium hobbyist could actually develope knowledge that the industry scientists have not already done. I just might have to try again.
 
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