Fish metabolism

[TbyZ]

Hi everyone, I'd like to know:
after a fish has been fed it digests & metabilises the food & excretes ammonia/ammonium from its gills.

Is this excretion a slow, even and ongoing process that lasts for a period of 12, 18, or even 24 hours after a single feeding?

Or is most of the ammonia that will be produced excreted over a much shorter period of time? 3 to 4 hours perhaps. And if so, how long after feeding would peak ammonia occur?

Appreciate any feedback.

 

[PatW]

Yes and no. The fish consumes food. Some of it passes through largely intact to be broken down later and other food is partially digested. The efficiency of digestion tends to be high for meat (meaning fish flesh in this case) and low for plant material like nori.

Anything that the fish excretes as ammonia pretty much has to be consumed, digested, absorbed as amino acids, metabolized and excreted. I would think excretion would be reasonably constant but a bit lower at night when the fish is asleep. But that is a guess. I would wager that no one has ever measured this. I would think that congress would take a really dim view of expending money on research of this nature.

 

[TbyZ]

I would wager that no one has ever measured this.

Oh, I bet someone has.
I've read a study that found peak DOCs occurred somewhere between 2 & 6 hours after feeding, or there abouts?

Some profesor Farnsworth in some university somewhere would have been funded at some time or another to measure it.

I might have to dig deeper.

 

[TbyZ]

Nitrogen metabolism and excretion

PJ Walsh, PA Wright

Patterns of Ammonia Excretion

https://books.google.com.au/books?i...sh metabolism, peak ammonia excretion&f=false


Using continue samples of ammonia (and urea) excretion in unfed blennies (Blennius pholis https://en.wikipedia.org/wiki/Lipophrys_pholis), however, Sayer detected distinct, well-defined peaks of ammonia release superimposed on a relative constant baseline. Notably, these peak release periods for ammonia coincide with bursts of urea discharge into the ambient water.


Ammonia and urea excretion in the amphibious teleost Blennius pholis (L.) in sea-water and in air

J Davenport. M.D.J Sayer

http://www.sciencedirect.com/science/article/pii/0300962986900629

Abstract

1. Blennius pholis (L.) demonstrates highly irregular excretion rates of urea and ammonia whilst immersed in sea-water. Usually peaks of ammonia and urea output coincide.

2. The blenny is predominantly ammoniotelic when in sea water, a mean output of 81.4% NH3 and 18.6% urea being recorded.

3. The blenny continues to excrete nitrogen during periods of aerial exposure, and remains predominantly ammoniotelic.

4. The major route of nitrogen elimination during emersion was via mucus secretions.


Nitrogen metabolism and excretion in the mangrove killifish Rivulus marmoratus I. The influence of environmental salinity and external ammonia.

Frick, Wright

https://www.ncbi.nlm.nih.gov/pubmed/11818414

Urea excretion (J(Urea)) (but not ammonia excretion, J(Amm)) displayed a diurnal pattern, with significantly less (75 %) urea excreted at night than during the day in both laboratory-reared clones and wild-caught killifish.

 

[Randy Holmes-Farley]

Why do you ask this question?

In a reef tank, many fish are also likely eating stuff constantly except when asleep.

 

[TbyZ]

Why do you ask this question?

In a reef tank, many fish are also likely eating stuff constantly except when asleep.

I feed my tank once a day & this is, by far, the greatest amount of food any of my fish consume at any time.

I wondered if there was a peak ammonia period, like there is a peak DOC period, after feeding, so I could tune my filtering for peak nutrient export.

 

[Randy Holmes-Farley]

Tune what sort of filtering?

 

[bif24701]

I feed my tank once a day & this is, by far, the greatest amount of food any of my fish consume at any time.

I wondered if there was a peak ammonia period, like there is a peak DOC period, after feeding, so I could tune my filtering for peak nutrient export.

I wouldn't worry about that. Corals need those things to feed. Keeping a steady filtering process through the day is best to keep the DOCs for building up.

 

[jason2459]

I feed my tank once a day & this is, by far, the greatest amount of food any of my fish consume at any time.

I wondered if there was a peak ammonia period, like there is a peak DOC period, after feeding, so I could tune my filtering for peak nutrient export.

Yes, I see ammonia swings daily and peaks late in the evening to very early morning around midnightish. I also see daily swings in PO4 as well.

https://www.reef2reef.com/threads/s...-for-the-established-tank-i-think-not.258297/

 

[Randy Holmes-Farley]

You see spikes after feeding, or just diurnal variations?

 

[jason2459]

You see spikes after feeding, or just diurnal variations?

Doesn't seem to be in sync with feedings. But I do feed a lot through out the day. 4 times a day I have an autofeeder drop pellets at 12pm, 3pm, 6pm, 9pm

I feed some meaty frozen foods at around 5pm and 8 or 10pm.

I will also place in 2 or more sheets of nori in the evening.

But I also see the same swings even when I'm away and those extra feedings don't happen.

 

[TbyZ]

Tune what sort of filtering?

Nothing too sophisticated.
I fitted a new algae scrubber a month or so ago. It has two screens.
Besides adjusting flow & photoperiod I have the screens illuminated at opposing times.
If I eventually settle on an illumination period, for each screen, that is greater than 12 hours there will be an illumination overlap.
So I was wondering if there was a period (like peak ammonia production) where it would be best to have this overlap, when the scrubbers filtering efficiency would be at it's peak.
From what I've read, some time during the day seems best.

 

[jason2459]

fwiw, I've gotten the best growth on my ATS since going 24/7 on it's lighting and increasing flow.

 

[TbyZ]

fwiw, I've gotten the best growth on my ATS since going 24/7 on it's lighting and increasing flow.

My growth is fine & it pulls out the nitrogen & phosphate beyond what I want well below 24 hour illumination.

I may only need to illuminate each screen for 9 hours. Not sure yet. Still tuning.

 

[jason2459]

Then just keeping it opposite your tanks photo-period is what I would do.

 

[TbyZ]

Then just keeping it opposite your tanks photo-period is what I would do.

I have one screen illuminated during the day & the other screen illuminated at night.
If I eventually need to illuminated each screen longer than 12 hours there'll be an illumination over-lap.
Maybe 2 hours where both are illuminated, & the scrubber is at peak efficiency.
Most ammonia is produced during the day, so I would set the 'over-lap' to occur during the day.

 

[jason2459]

...
Most ammonia is produced during the day, so I would set the 'over-lap' to occur during the day.

Why do you think that? If you really want to see what your system is doing ammonia wise the seneye monitor seems sufficient which is what I linked to above. .

 

[TbyZ]

Why do you think that? If you really want to see what your system is doing ammonia wise the seneye monitor seems sufficient which is what I linked to above. .

from what I've read peak release periods for ammonia coincide with bursts of urea discharge into the ambient water and fish excrete significantly less urea at night.

 

[jason2459]

from what I've read peak release periods for ammonia coincide with bursts of urea discharge into the ambient water and fish excrete significantly less urea at night.

Not my experience since monitoring it. Was the research on small closed systems like our Aquariums?

 

[TbyZ]

If you really want to see what your system is doing ammonia wise the seneye monitor seems sufficient which is what I linked to above. .

Every tank is different. What you feed; when you feed.
I don't have a seneye. Maybe I'll get one?