Ammonia produced by X pounds of fish?

[J. H.]

I wouldn't say 100%. Fish have extremely elevated output of ammonia after eating. Estimates I've seen are that 60% of this increase is directly from food. But even starved fish produce ammonia. Studies show that barring stress, starved fish will produced a low for continuous amount of ammonia.

Imo, this is likely internal metabolism. Fish are composed of proteins and when their cells are damaged or die, that would lead to a release of ammonia. Stress, unusually activity from swimming leads to increases in this level of release.

So, food protein is the primary source of the "surplus" ammonia. Studies I've seen claimed 60-80% was directly from food recently consumed.

Ultimately, I would suggest 100% is from food, because the muscle fibers (tissue) in the fish is a direct result of food. Fish can't generate their tissues from water and air.

Yes, but the rule still has to follow "N in = N out". The nitrogen either entered the tank when you put the fish in or fed it previously. It may have been locked up in the fish's body, but it was there all along. Your aquarium is pretty much sealed. More or less anything that is in there is there because you put it there. Rotting plants or inverts can create ammonia as well, but again, you put that nitrogen in the tank when you put in the inverts/plants or fed them to allow them to grow/reproduce. I once lost a whole tank this way. I had finrot, and treated with Melafix, which in turn killed all my snails - instant tank crash. Everything was dead by the time I came home from school the next day

 

[J. H.]

I wouldn't say 100%. Fish have extremely elevated output of ammonia after eating. Estimates I've seen are that 60% of this increase is directly from food. But even starved fish produce ammonia. Studies show that barring stress, starved fish will produced a low for continuous amount of ammonia.

Imo, this is likely internal metabolism. Fish are composed of proteins and when their cells are damaged or die, that would lead to a release of ammonia. Stress, unusually activity from swimming leads to increases in this level of release.

So, food protein is the primary source of the "surplus" ammonia. Studies I've seen claimed 60-80% was directly from food recently consumed.

Ultimately, I would suggest 100% is from food, because the muscle fibers (tissue) in the fish is a direct result of food. Fish can't generate their tissues from water and air.

Yes, but the rule still has to follow "N in = N out". The nitrogen either entered the tank when you put the fish in or fed it previously. It may have been locked up in the fish's body, but it was there all along. Your aquarium is pretty much sealed. More or less anything that is in there is there because you put it there. Rotting plants or inverts can create ammonia as well, but again, you put that nitrogen in the tank when you put in the inverts/plants or fed them to allow them to grow/reproduce. I once lost a whole tank this way. I had finrot, and treated with Melafix, which in turn killed all my snails - instant tank crash. Everything was dead by the time I came home from school the next day

 

[Drstrangelove]

Yes, but the rule still has to follow "N in = N out".

I hope I didn't contradict that in my post.

But yes, I agree. Nitrogen atoms, while certainly in the tank in gas form, don't become ammonia or protein on their own. Those compounds are added to the tank from an external source or created by metabolism (catabolism) from living things inside the tank. Predominantly fish and primarily from food.

 

[Hendre]

So stocking 5kg of fish with twice the feed of 10kg of fish will have a similar bioload?

 

[J. H.]

So stocking 5kg of fish with twice the feed of 10kg of fish will have a similar bioload?

It will have twice the bioload.

 

[Hendre]

It will have twice the bioload.

Sorry that's what I meant to say, was late when I posted.

So someone could stock a load of fish if they feed sparsely?

 

[J. H.]

Sorry that's what I meant to say, was late when I posted.

So someone could stock a load of fish if they feed sparsely?

According to what was said here, if the 'load of fish' could live okay on that sparse feeding, yes. But once some fish begin to starve, they will release ammonia from nitrogen stored in their bodies and stress hormones, and the competition for food will cause aggression... it would be a very delicate balance.

 

[Hendre]

Just in theory

I'm thinking of building a calculator for various concepts in aquaria for my IT practical task. Nitrates included which is why I'm so curious here

 

[Drstrangelove]

I would add a technical nitpicky caveat...

The maintenance level for an adult fish varies, but .75 - 1.25% of body weight per day has been found for various species. (Obviously each is different and high temp tanks with active fish might be different from low temp tanks with sedentary fish.)

Surplus goes to activity (or waste) and surplus over that goes to growth (or waste.) The food conversion ratio (FCR) tells you how much food it takes to add a certain amount of weight to a fish. The FCR assumes normal temps, water conditions, activities and varies according to temp, age, species, and type of food. Normal ranges iirc are ~ 3-10:1, but again that varies a lot based on food, species and age.

Younger fish are smaller of course but like human kids, consume a lot of calories per pound. A typical fry to juvenile fish might expect to get way above 5% of body weight per day on average for many weeks or months.

So, e.g., feeding 10kg of fish with twice the amount of food as 5kg will be twice the bioload assuming the fish are the same species and the same age. However, this might not be true if 5 kg are one species and the 10 kg are another, since different species have different FCRs. I.e., it might not be twice the bioload because more food will be retained in some fish versus others.

 

[Hendre]

If I was to do a calculator, I'd just do it based off of dry weight of food and make a rough assumption or go for the minimum and maximum protein to N values?