Possible method of estimating ammonia production from food

Joshaeus

Member
HI everyone! I was doing research yesterday and discovered that ammonia is produced primarily by the digestion of proteins (or, more specifically, of the amino acids composing those proteins), and I found no indication that fats or carbs are converted to ammonia. Amino acids vary in size, but their molar mass is typically 110 grams per mol, and the equation for digesting them generally looks something like this; 2NH2CHRCOOH (amino acid) + O2 2CROCOOH + 2NH3 (ammonia)

Ammonia has a molar mass of 17 grams per mol, so we can estimate how much ammonia will be added if we know the mass of the food going into the tank, what percent of that is protein (which is listed on all fish food labels), and the tank's size. For example, I have some omega 1 pellets that are 42% protein, and I found that a ml of these pellets in a scoop is about .32 grams. To calculate how much ammonia that would add;
- Multiply .32 by how many ml of food you are adding (in this case, 1).
- Multiply the mass of food (.32 grams, per above) with the percentage that is protein (in this case, 42%, or .42). This gives us .1344 grams of protein that will eventually be converted to ammonia.
- Divide .1344 grams by the molar mass of amino acids (110 grams/mol). This reveals that we have added about .00122 mols of amino acids to the tank.
- Multiply that value by ammonia's molar mass of 17 grams per mol. This reveals that we have added .02077 grams of ammonia to the tank.
- Divide the above value by the tank's volume in milliliters (one gallon of water is about 3,780 ml) and multiply the result by 1,000,000 to find how many parts per million (ppm) of ammonia this would add to the tank. For example, if I added the above .32 grams of these omega 1 pellets to a 10 gallon, that would be .02077/37800 = .00000054947 = .54947 ppm ammonia.

So, with the possible exception of the unusual case where a fish is being underfed, we can estimate how much ammonia is going into the tank based off the food we are feeding.

This can also be extended to nitrite and nitrate; during the nitrogen cycle, ammonia is converted to nitrite (No2) and nitrate (NO3), with every mol of ammonia converted in this fashion becoming a mol of nitrite and eventually nitrate. Nitrite has a molar mass of 46 grams per mole, and nitrate 62 grams per mol, so we can estimate the amount of nitrite/nitrate we add to a tank in a similar fashion to the above, with the exception of replacing ammonia's molar mass with that of nitrite/nitrate (for the sake of argument we will assume that none of the ammonia is consumed by plants and algae prior to being converted). Doing so with the above example gives .05612 grams nitrite and .07564 grams nitrate, which - in a 10 gallon tank - is about 1.485 and 2.001 ppm nitrite and nitrate respectively.

I am hoping that (A) my research is correct, and (B) that this observation is useful for future tank endeavors, both my own and those of others on this forum. Thanks for reading
 

girlwithmanyeyes

Member
While I think you are correct in the situation of adding food to a tank - I don't see where you are accounting for those amino acids that are staying in the fish. The majority of protein consumed will stay inside and be used to grow new tissue/cells.

I like the way you think though
 
  • Thread Starter

Joshaeus

Member
girlwithmanyeyes said:
While I think you are correct in the situation of adding food to a tank - I don't see where you are accounting for those amino acids that are staying in the fish. The majority of protein consumed will stay inside and be used to grow new tissue/cells.

I like the way you think though
Very true! I was not thinking about that point...it's a good upper bound at least, though.

EDIT: I did some research and found that fish use food quite efficiently...1.1 kg of feed, for example, is sufficient to raise a 1 kg salmon, implying that about 90% of their feed is incorporated into their tissues. I don't know whether aquarium fishes in general are similarly efficient (I know seahorses and pipefish are not), but I guess it's safe to say that if the fish are not overfed the food will not produce nearly as much ammonia as I calculated.
 

Momgoose56

Member
Joshaeus said:
HI everyone! I was doing research yesterday and discovered that ammonia is produced primarily by the digestion of proteins (or, more specifically, of the amino acids composing those proteins), and I found no indication that fats or carbs are converted to ammonia. Amino acids vary in size, but their molar mass is typically 110 grams per mol, and the equation for digesting them generally looks something like this; 2NH2CHRCOOH (amino acid) + O2 2CROCOOH + 2NH3 (ammonia)

Ammonia has a molar mass of 17 grams per mol, so we can estimate how much ammonia will be added if we know the mass of the food going into the tank, what percent of that is protein (which is listed on all fish food labels), and the tank's size. For example, I have some omega 1 pellets that are 42% protein, and I found that a ml of these pellets in a scoop is about .32 grams. To calculate how much ammonia that would add;
- Multiply .32 by how many ml of food you are adding (in this case, 1).
- Multiply the mass of food (.32 grams, per above) with the percentage that is protein (in this case, 42%, or .42). This gives us .1344 grams of protein that will eventually be converted to ammonia.
- Divide .1344 grams by the molar mass of amino acids (110 grams/mol). This reveals that we have added about .00122 mols of amino acids to the tank.
- Multiply that value by ammonia's molar mass of 17 grams per mol. This reveals that we have added .02077 grams of ammonia to the tank.
- Divide the above value by the tank's volume in milliliters (one gallon of water is about 3,780 ml) and multiply the result by 1,000,000 to find how many parts per million (ppm) of ammonia this would add to the tank. For example, if I added the above .32 grams of these omega 1 pellets to a 10 gallon, that would be .02077/37800 = .00000054947 = .54947 ppm ammonia.

So, with the possible exception of the unusual case where a fish is being underfed, we can estimate how much ammonia is going into the tank based off the food we are feeding.

This can also be extended to nitrite and nitrate; during the nitrogen cycle, ammonia is converted to nitrite (No2) and nitrate (NO3), with every mol of ammonia converted in this fashion becoming a mol of nitrite and eventually nitrate. Nitrite has a molar mass of 46 grams per mole, and nitrate 62 grams per mol, so we can estimate the amount of nitrite/nitrate we add to a tank in a similar fashion to the above, with the exception of replacing ammonia's molar mass with that of nitrite/nitrate (for the sake of argument we will assume that none of the ammonia is consumed by plants and algae prior to being converted). Doing so with the above example gives .05612 grams nitrite and .07564 grams nitrate, which - in a 10 gallon tank - is about 1.485 and 2.001 ppm nitrite and nitrate respectively.

I am hoping that (A) my research is correct, and (B) that this observation is useful for future tank endeavors, both my own and those of others on this forum. Thanks for reading
That's just TOO much OCD for me lol! I LIVE with OCD's, raised OCD's, feed OCD's, clean up after OCD's (well not much cleaning...they have OCD after all lol!).
They're all Mechanical, software, physics, optics, & civil Engineers-my tank is my escape from OCD thank you very much! Haaaahaha!
 

FishRFriendz

Member
Joshaeus said:
EDIT: I did some research and found that fish use food quite efficiently...1.1 kg of feed, for example, is sufficient to raise a 1 kg salmon, implying that about 90% of their feed is incorporated into their tissues. I don't know whether aquarium fishes in general are similarly efficient (I know seahorses and pipefish are not), but I guess it's safe to say that if the fish are not overfed the food will not produce nearly as much ammonia as I calculated.
I wonder if the efficiency may change with the age of the fish. When they're young and growing fast it must be very efficient, but at adult size, where would all the protein go if the fish isn't getting larger?
 
  • Thread Starter

Joshaeus

Member
Depends...how much are they eating? Unlike most mammals, fish never stop (slowly) growing, so as long as they are not significantly overfed I assume most of the protein would still be incorporated into the fish.
 

AvalancheDave

Member
FishRFriendz said:
I wonder if the efficiency may change with the age of the fish. When they're young and growing fast it must be very efficient, but at adult size, where would all the protein go if the fish isn't getting larger?
They grow slower so they eat less?

There are a lot of formulas in aquaculture for ammonia from quantity of food and % protein. Feed conversion ratio by age. I know they feed less to older fish, too.

It's not economical to keep animals after the rapid growth period. That's why a lot of food animals are slaughtered fairly young. Trees, too.
 

H Farnsworth

Member
Honestly youd have to do some species only tanks and develop metabolic rate models for each species. Then a just food tank as a negative control. I imagine in the short term the just food tank would have higher nitrogen levels from X amount of food where as the actual fish tanks would catch up after 72 hours.

Or you could take your community tank, fast the tank for a few days then get nitrogen levels to 0. Add a measured amount of food then don't feed again for a week. You could measure nitrogen throughout the week and possibly come up with something. Functional biology is a messy game.
 

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