Nitrogen Cycle Equation & Fish Waste

[SexyFishKeeper]

Hi all,

Thought I'd throw this on for debate...

I was doing the usual surfing the net and found the following link http/www.aquariumfish.net/information/filtration.htm. On there it outlines the equation for the nitrogen cycle...

4 NH3 (Ammonia) + 7O2 (Oxygen) = 4NO2- (Nitrite) + 6H20 (Water) + Energy

2NO2- (Nitrite) + O2 (Oxygen) = 2NO3- (Nitrate) + Energy

From that I'd expect 4ppm of Ammonia to create 4ppm Nitrite which would then turn into 4ppm Nitrate.

Therefore, if that equation holds (what do you think?), I'm going to see if using the Nitrate outputs I can calculate the amount that my fish produce in Ammonia.

Has anyone ever done such a study? Do you think it's worth while doing?

 

[andywg]

How will you be sure the ammonia/nitrate produced is from the fish alone and not from decomposing food that is uneaten?

I have little doubt that some sort of study into nitrate and ammonia production has been performed to allow fish farms to better understand how they can stock.

 

[SexyFishKeeper]

How will you be sure the ammonia/nitrate produced is from the fish alone and not from decomposing food that is uneaten?

I know what you mean andywg, guess I'll have to be careful and not over feed.

 

[rdd1952]

Also, the amount of waste they produce will be in direct proportion to the amount of food you give them, even if they eat it al and none decays to produce ammonia on it's own. For instance, if you feed them twice a day versus once a day (and they eat all the food each time), they will produce more waste. Also things like decaying leaves can produce ammonia. With our limited abilities, it would be difficult to calculate how much ammonia our fish produce.

 

[andywg]

Also, the amount of waste they produce will be in direct proportion to the amount of food you give them, even if they eat it al and none decays to produce ammonia on it's own. For instance, if you feed them twice a day versus once a day (and they eat all the food each time), they will produce more waste. Also things like decaying leaves can produce ammonia. With our limited abilities, it would be difficult to calculate how much ammonia our fish produce.

I am not so sure I entirely agree on this.

While the amount of food the fish are processing will definitely have an effect on the level of ammonia production, I seem to recall reading, both on here and in my icthyology texts, that somewhere around 80% of the ammonia excreted is from the osmoregulation process and not digestion.

A couple of the papers that may help you (if you have access) are listed below:

http/www.ncbi.nlm.nih.gov/sites/entrez?c...p;dopt=Citation

http/www.springerlink.com/content/q85v605821187136/

 

[Bignose]

If you accurately weigh how much food you give your fish, you should be able to estimate the production from the food you give them.

Calculate the amount of protein the food, 40% is typical -- this should be on the food canister

16 % of proteins are nitrogen

(food mass)*0.40*0.16 = mass of nitrogenous waste excreted per day.

Take the estimated mass and divide it by the volume of the tank to get the concentrations (ppm is a concentration).

It would be interesting to compare the two numbers, the estimate from the food, and the estimate from the nitrate measurements. Hope you post the results when you get them, SFK.

 

[iankent]

4 NH3 (Ammonia) + 7O2 (Oxygen) = 4NO2- (Nitrite) + 6H20 (Water) + Energy

2NO2- (Nitrite) + O2 (Oxygen) = 2NO3- (Nitrate) + Energy

From that I'd expect 4ppm of Ammonia to create 4ppm Nitrite which would then turn into 4ppm Nitrate.

Hi SFK - the chemical equation isn't that simple, as you need to take into account molecular mass to work out how much Ammonia becomes Nitrite, and how much Nitrite becomes Nitrate.

From my calculations, the ratio's are:
1ppm ammonia becomes 2.701352ppm nitrite
2.701352ppm nitrite then becomes 3.640805ppm nitrate

In the process, you'll be using up 1.878905ppm oxygen and 1.057821ppm water (if you're using mg/L then just multiply the ppm values by the number of litres in your tank to work out the actual mg's of each chemical), and producing 0.29592098ppm hydrogen