How Much Ammonia Can A Fish Produce?

[businesslamb]

I guess this question arises from the various questions and discussions about stocking levels I have seen on the site. On a simple level the amount of stock a tank can hold is dependant on the amount of ammonia the fish produce (AP) and how much ammonia the bacteria on the filter can consume (AC). If AP is bigger than AC then you are in trouble.
Since it is tricky to measure how many bacteria a given filter can hold (because all filters are going to perform differently under a large number of variables) then guidelines like inches per gallon are used but has anyone ever attempted to measure how much ammonia a typical fish (eg a 1 inch Zebra danio) produces in a day? Is it 1mg, 10mg, 100mg? Also do 6 one inch tetras produce more or less waste than one 6 inch cichlid (less I would guess but how much less? 10%, 50%?)
There is much more to this of course since there are a number of variables involved such as how active the fish are, what the temperature is, how much food is given and of what type etc but I was wondering if any one had any idea.

Cheers

Businesslamb

 

[jayjay]

i've thought of it but never really into the extenet that i'd test it or anything but this maight be something to do with it

http/www.practicalfishkeeping.co.uk/pfk/pages/ammonia.php

 

[Bignose]

There are numerous variables, I might try to search through the web of science (database of journal articles) later when I have time. But, temperature, food component, and fish activity all come to mind.

But, as a general guide, the more mass a fish has, the more ammonia it is going to excrete. However, with regards to the inch per gallon rule, most people can esitamte the length of their fish pretty well, while it is not easy at all to estimate the mass. The fish would have to be wieghed. Estimating three lengths to get a volume (length x width x height) and then mulitplying by a denisty to the get the mass would be full of errors. I would bet really good money that not all fish have the same density, too. So, errors in 4 numbers multiplied together become very large, whereas if you underestimate one length, it is probably not so bad.

Besides, I think that most regular forum members know all about the limitations of the inch per gallon rule, so it is kind of a moot point anyway.

Finally, I'd like to point out that it is not the amount of ammonia that is present that determines how much bacteria is present, but rather the rate at which ammonia is produced which determined the amount of bacteria. Specifically, the bacterial colony will grow until the rate the colony processes ammonia is the same as the rate at which ammonia is produced by the bio-load.

 

[businesslamb]

You are correct it is the rate of production which is important and I would guess this would fluctuate considerably over a 24 hr period, peaking after feeding and being lowest after lights out.
But “rate of production of ammonia: variations by fish species” sounds more like the title of a scientific article and isn’t quite as catchy as How much ammonia can a fish produce?
There is an article on the pfk website which mentions “carrying capacity”http/www.practicalfishkeeping.co.uk/pfk/pages/show_article.php?article_id=125 but unfortunately I don’t have access to Bull. Jap. Soc. Sci. Fish .
So that comes back to my original question how much ammonia does a fish produce (per day) Is it 1mg, 10mg, 100mg? If you wanted to measure I guess you could put a fish in a bare unfiltered tank and measure the ammonia levels after 24hrs, that would be somewhat cruel as you would be slowly poisoning it. More ethically you could sequester the ammonia in some manner (ion exchange? ) and then recover and measure the ammonia. Or you could measure the nitrate produced in a bare filtered tank and making the assumption that all the ammonia produced ends up as nitrate. Perhaps I should write to pfk, Somewhat different to the usual questions about “how big a tank do I need for this red tailed catfish I bought”

Cheers

Businesslamb

 

[Bignose]

Every article I could locate only has anything to do with one specific species. For example:

MEDALE F, BRAUGE C, VALLEE F, et al.
"EFFECTS OF DIETARY-PROTEIN ENERGY RATIO, RATION SIZE, DIETARY ENERGY-SOURCE AND WATER TEMPERATURE ON NITROGEN-EXCRETION IN RAINBOW-TROUT"
WATER SCIENCE AND TECHNOLOGY 31 (10): 185-194 1995

and almost every single species was not of interest to aquarists, but to fish-farmers. Makes sense, the fish farms are where the money is at in regards to fish.

 

[Majjie]

I've been thinking about this

Surely all the fish in a tank can only produce ammonia (NH3) from the food they eat.
A small tub of dry fish food contains between 20 and 50g food (TetraMin/Interpet Liquifry powder)
The protein content is between 44 and 47% (on my 6 kinds of dry food) - lets say 50%
The average nitrogen (N) content of a protein is 16% (check on Google)

Lets say, for the sake of argument that you put 300mg of food into your tank a day i.e. a small tub of TetraMin would last just over 2 months (just for that one tank) - worst case scenario!
50% is protein and 16% of that is N - total of 24mg N per day

The fish are going to use most of the N (a turbot apparently only excretes up to 7.5% of dietary N intake as ammonia) - but lets assume that tropical fish are horribly inefficient and only use 50% of their food N. 12mg of excess N per day is available to make NH3.

Now lets look at the filter. During fishless cycling we put household ammonia into the tank (or, at least I do). When my tanks were fully cycled they could remove at least 10 drops of household ammonia from the tank overnight (15hours). The household ammonia is a solution of 9.5% NH4OH. Lets assume that a drop is 0.025ml (it's probably bigger) - that means that the filter can remove 23.75mg NH4OH in 15 hours, or about 38mg per day. 38mg of NH4OH contains about 15mg N (molecular weight 35/atomic weight 14).


Conclusion: the filter is more than capable of dealing with all the NH3 that is likely to be produced

Unless your fish are chomping thru the whole plant content of the tank each day (low protein content in vegetables!); lots of plants/snails/fish are dying each day; you're chucking in a whole tub of food each day; or you kill off the filter bacteria in some way - the capacity of the filter is unlikely to be a problem

I've always believed that it is the oxygen carrying capacity of the water that is the limiting factor on stocking levels, not the filter - hence the limit of 1in. fish per 12 sq.in. surface area. I know a lot of you on here will disagree, though. I'd never heard of the 1in. fish per US gallon rule before I joined here - by that measure all my tanks are overstocked

 

[Majjie]

Wot - no comments! You're no fun

 

[andywg]

OF course the inch per gallon has you overstocked. It has almost every experienced aquarist overstocked. It is used as a guide for people new to the hobyy who aren't as likely to be as rigid in their upkeep of the tank, nor in their ability to spot problems with the tank.

The processing level of ammonia will almost never be the defining point in how many fish a tank can hold, and I would be surprised if oxygen is (provided you are not going planted or have zero surface movement).

The most common factor is the rate at which nitrates build up. As they rise, the fish can begin to suffer. You can massivly overstock a tank but connect it to huge filtration to handle the ammonia (and nitrites) as well as providing a huge amount of gas exchange, but the nitrates will rise quickly and affect the tank.

This is where the limiting factor on a tank tends to be (as well as actually having enough physical room for a fish to swim in).

 

[Majjie]

OK. Thanks for the reply.

I really meant a comment on all my calculations.

Sorry if I'm sounding like an uppity newcomer. You experienced guys must get fed up with it. Like I say - I'd never come across the 1" per USg rule before.

 

[TammyLiz]

OF course the inch per gallon has you overstocked. It has almost every experienced aquarist overstocked. It is used as a guide for people new to the hobyy who aren't as likely to be as rigid in their upkeep of the tank, nor in their ability to spot problems with the tank.

The processing level of ammonia will almost never be the defining point in how many fish a tank can hold, and I would be surprised if oxygen is (provided you are not going planted or have zero surface movement).

The most common factor is the rate at which nitrates build up. As they rise, the fish can begin to suffer. You can massivly overstock a tank but connect it to huge filtration to handle the ammonia (and nitrites) as well as providing a huge amount of gas exchange, but the nitrates will rise quickly and affect the tank.

This is where the limiting factor on a tank tends to be (as well as actually having enough physical room for a fish to swim in).

This is really the point here--ammonia doesn't really matter in a cycled tank as long as biological filtration is adequate. Its the nitrate that builds up as a byproduct that really matters. The more waste (aka fish) in a tank, the more water changes will be needed to keep up with their waste. As far as stocking goes, there is a point where you can reach the balance between the work involved and the number of fish you want. If you're willing to do daily 50% water changes you'll be able to keep a lot more fish in the same volume of water as someone who can't bear to put their hands in the tank more than once a month. In my opinion, if you want extra fish, it's best to just get an extra tank, or a larger one. That way you're not walking such a tight line to keep them healthy.

 

[businesslamb]

Hi Majjie,
I can’t comment on the veracity of your calculations, but there is a pretty big assumption about the ability of fish to assimilate nitrogen. Your calculation does though give a ballpark figure though which is at least a start and it is true that total nitrogen output cannot exceed that in the food given.
When I did my fishless cycle the filter was able to deal comfortably with 135mg of ammonia (ie 0.5ml of concentrated aqueous ammonia) in 24hrs. This obviously provided enough bacteria to comfortably deal with my initial stock as of three inches of fish as at did I detect any ammonia.

I should point out that I’m not asking the question with the intention of pushing my stocking level to the limit. Indeed far from it I am currently at about 15 inches (When fully grown it will be about 20 inches) of fish in a 27.5 (uk) gal tank and I’m in no great hurry to add any more. It was really only something that I was curious to know. It’s the sort of information that would be when doing a fishless cycle as you could work out from your planned initial stocking level the minimum amount of ammonia you would need to add per day to give your filter an adequate ammonia processing capacity.

The funny thing about nitrate levels is that I’m using a Juwel nitrate removing sponge in the filter and my nitrate level is consistently around 10 ppm. The nitrate level in my tap water is around 30ppm so whenever I do a water change I’m actually making the nitrate level worse!

Cheers

Businesslamb

 

[TammyLiz]

The funny thing about nitrate levels is that I’m using a Juwel nitrate removing sponge in the filter and my nitrate level is consistently around 10 ppm. The nitrate level in my tap water is around 30ppm so whenever I do a water change I’m actually making the nitrate level worse!

That's interesting. At the expense of possibly sounding ignorant and stupid, I'd like to ask what exactly they are made of to absorb nitrate. I've never heard of them before.

 

[businesslamb]

I have to be honest and say I don't know. It appears to work as a chemical scavenger i.e lasts for a short period (6-8 weeks depending on nitrate production) and can only remove a finite amount of nitrate.
I asked Juwel how it works and I was surprised by their reply (below) as they claim it works by bacterial action. As a scientific researcher I would have to say I’m somewhat sceptical of their claim but it does seem to work.

Dear Sir,

Please be informed that the nitrate sponge does not work like a carbon sponge.
The nitrate sponge works with nitrate feeding bacteria which are alive app. 6
weeks. Then you may replace the sponge or, if your water quality is very good,
you can use the green sponge as a second coarse one.

Hope this helps you. Best regards,
JUWEL Aquarium GmbH & Co. KG
SERVICE
Birgit Fischer

 

[TammyLiz]

Hmm...I thought nitrate feeding bacteria were anaerobic and thats why we have difficulty creating a closed system in an aquarium since an anaerobic environment within the little ecosystem is likely to do more harm than good? I'm feeling the scope of my lack of knowledge here. I'm going to have to look into it. I wish they had given you a better answer. I agree it seems that it must be at the very least incomplete.

 

[andywg]

I believe they are actually anoxic, meaning they require very little oxygen to no oxygen but will generally require a slight amount of oxygen to filter through to keep the process running smoothly.

But you are correct, there is no way they can work as Juwel says, though considering how awful the Juwel filter is, it doesn't surprise me that they don't know how this works.

Plus, how do they ship the sponge? If it dries out, how does the aquatic bacteria survive?

I would still put forward that they are a chemical filter that is absorbing a certain amount of nitrate and then stop.