Fishless Cycling Question

[brian2708]

Hi.

I am doing a fish-in cycle currently, so this doesn't really apply to me however I'm just really intrigued about the chemistry of things.

So in a fishless cycle, we end up injecting the tank with upto 5ppm ammonia, so we can establish the bacteria that carrys out the cycle, however, I consider my tank to be fairly well stocked, and have never had my ammonia go above 0.25ppm.

Isn't establishing a filter to handle 5ppm ammonia a bit excessive in that when you add fish (and people recommend adding a small number), you will probably starve the majority of the bacteria anyway?

Maybe I'm just not understanding something here.

 

[Bignose]

A fully stocked tank will make 2 to 3 ppm of ammonia per day, some even as much as 4 ppm. The reason a healthy tank should see zero ammonia, is because if everything is working right, the rate of production of ammonia by the fish is the same as the rate of consumption of ammonia by the bacteria. That means as soon as some ammonia is made, it is consumed.

Another reason 5 ppm seems to be a good number is that it is over the largest possible total, but at most it costs you one extra day of fishless cycling to hit that. The cycling bacteria are pretty slow growing compared to most bacteria, and the general rule of thumb is that the cycling bacteria at tropical temperatures double in number every 24 hours given sufficient food. Which means that if today you have a colony that handles 5 ppm, the day before it could only handle 2.5 ppm. 2.5 ppm is good enough for a moderately stocked tank, but not a slightly overstocked one. So, you wait one more day, and then you have a colony that can handle all but the most extreme (and inadvisable) situations.

here are a few old threads you may like to read over:

http/www.fishforums.net/index.php?/topic/226664-why-water-changes-during-cycling-are-good/ a lot more on what happens during cycling in terms of input and output for the ammonia oxidizing bacteria

http/www.fishforums.net/index.php?/topic/242818-how-much-bioload-does-1-fish-produce/ a calculation to show how much ammonia fish can produce

 

[brian2708]

Perfect. Very interesting Read. Thanks for that Bignose.