Size - eye versus stomach

Jaysee

You often hear how a fish's stomach is the size of it's eye. Working on a fishing boat, I've got a lot of experience examining fish stomachs, and I've always maintained this to be an inaccurate assessment. I just assumed that, because of proportions, the aquarium fish would have stomachs much larger than their eye since larger fish do.

Soooo, this is (was) a flame tetra. The eye is on the left, the stomach is on the right. flame 003.JPG
 

Shine

Seems your hypothesis was correct

Glad to see that one disproven. I've been repeating that one for a while now.
 

psalm18.2

I always doubted that theory myself. I'd like to see comparison w/ a larger fish like bass.
 

Akari_32

Gross lol

I never really thought that was true, anyway. How can a 5 ft Grouper have a stomach the size of a baseball?? Just sayin' XD


*edit* Ninja'd by Psalm I like how we are on the same page XD
 

Jaysee

I'll snap some pics at work this weekend.
 

toosie

Great work Jaysee. Looking forward to those other pics. ewwwww but I still want to see.
 

soltarianknight

I coulda just thrown a pic of catfish guts on here, they have a stomach the size of their heads lol.
 

Jaysee

Yeah, but the last time I brought this up the argument was that aquarium fish were different.
 

psalm18.2

Yeah, but the last time I brought this up the argument was that aquarium fish were different.

Why? That makes no sense, fish are fish.
 

Akari_32

Yeah, but the last time I brought this up the argument was that aquarium fish were different.

I don't see why they would be. Fish are fish


*edit* Dang you Psalm!!!
 

Jaysee

Why? That makes no sense, fish are fish.

One thing I've learned over the years, is that an argument doesn't have to make sense.....
 

Lucy

Ewwwww.
Interesting but ewww none the less.

I always assumed the eye/stomach thing was true.
 

soltarianknight

One thing I've learned over the years, is that an argument doesn't have to make sense.....

never forget this kiddies
 

psalm18.2

I don't see why they would be. Fish are fish


*edit* dang you psalm!!!

lol!
 

sirdarksol

I don't see why they would be. Fish are fish

Size. Different parts of the body grow at a different ratio, depending on the importance of that organ to the critter. For example, a flame tetra's eye appears to be about 1/4 of the size of the stomach. Though I've never cleaned a fish, I'm guessing that an adult sunfish's stomach is quite a bit larger than 4x the size of its eye.

Now, playing devil's advocate (because it's what I do), while the statement about eye/stomach size is obviously false, this doesn't entirely render it useless.
We're looking at the outside of the stomach, whereas the statement is discussing how much a fish should eat. This means that we should first consider the fact that we're thinking of the empty space inside of the stomach, not the external size of the stomach. We should second consider the fact that it isn't healthy to have a completely and continuously full stomach*.
So, yeah, fish's stomachs are larger than their eyes. On the other hand, saying "small aquarium fish should be fed about as much food as the size of their eyes" would be pretty accurate, presuming you're feeding on a daily basis.

*Caveat. This may not be true for all fish, particularly algae grazers like otos, who feed on relatively calorie-light foods. But then, we're primarily talking about how much flake/crisp/pellet to feed our fish.
 

Jaysee

We're looking at the outside of the stomach, whereas the statement is discussing how much a fish should eat. This means that we should first consider the fact that we're thinking of the empty space inside of the stomach, not the external size of the stomach.

Since the stomach is elastic and designed to stretch to accommodate food, of what relevance is the interior volume of an empty stomach?
 

sirdarksol

If an organism is eating on a regular basis, the stomach shouldn't be stretched all that much during those meals.

The stomach stretches because not every creature gets to eat regularly, so nature gave us the ability to gorge when we get a windfall in lean times.
 
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Jaysee

So your saying that the stomach only expands when the animal isn't eating regularly? That it's static otherwise? If you were only feeding an eye ball portion or enough to fill the interior volume of an empty stomach, then yes I imagine it wouldn't stretch very much....
 

soltarianknight

I think we should recognize that all fish have different needs as far as food consumption. Catfish in general seem to prefer larger meals or to gorge themselves, plecos(also cats) will literally eat and poo at the same time.... Smaller tetra should probably eat small amounts more often. bettas and similar species will typically eat periodically through out the day so 1-2 feedings should do them fine, and so on, and so on. Its as jaysee says
we live in the fishkeeping Age of Enlightenment
XP.

Which means not only breaking down and desolving the simplistic and vague rules of the past, like the "1 inch per gallon" and "eyeball stomach", but it also means we need to start recognizing the individuality of species needs and not clumping them under one phrase or rule. We can do SO much better then that SO MUCH.


Ok my peace talk I through, now I need to go gargle.
 

Jaysee

And some fish have larger eyes than others
 

Akari_32

And some fish have no eyes
 

psalm18.2

I've seen bigger than the eyeball.
 

jerilovesfrogs

wt....was that your tetra? and you cut him up! yeah ok...I am guessing he was dead, but still....kind of eww. haha. actually it's pretty precise of you....that is a very small fish. and yup, his stomach is bigger than his eye.
 

Jaysee

It was my neighors tetra - I snuck in his house and took the fish - Like I'd cut up my OWN fish. Sheesh
 

soltarianknight

You know I worked really hard on that mini-speech...
 

Akari_32

It was my neighors tetra - I snuck in his house and took the fish - Like I'd cut up my OWN fish. Sheesh

 

jerilovesfrogs

hopefully your neighbors dead tetra ;D
 

catsma_97504

While I never assumed the eye and the stomach was the same size of any animal, the statement to feed enough food based on the size of the eye can be very helpful to avoid overfeeding our fish.
 

lea

Great to see an actual comparison to set this one straight.

Naturally, eye size and stomach size vary greatly depending on fish size and species. Obviously a grouper has a far smaller eye than its gut, but an ox-eye herring might be closer in size.

Myth busted - nice once Jaysee
 

Jaysee

Thank you

I had an interesting occurrence at work today. I was cutting up a sundial for bait, so I did another comparison. HOWEVER, In ALLLLLLLLLLLLL the fish I've filleted over the years, I've never seen parasites spill out.....

Pics are comparisons - the first is obvious (pic taken after the stomach was emptied). The second is the eye, the stomach contents, and the parasites. Tapeworms?CIMG0094.jpgCIMG0096.jpg
 

soltarianknight

looks like Tapes to me.
 

Jaysee

Here's a flounder

CIMG0097.jpg
 

Butterfly

Good job Jaysee! Now that you've done away with a simple(although incorrect) way to get across to new aquarist not to over feed their tank we need to figure out a way to convey that concept without incorrect comparisons.

What do you think would be a good way to do this? Don't want to hijack your thread so we can move this question if need be.
Carol
 

Jaysee

Good job Jaysee! Now that you've done away with a simple(although incorrect) way to get across to new aquarist not to over feed their tank we need to figure out a way to convey that concept without incorrect comparisons.

What do you think would be a good way to do this? Don't want to hijack your thread so we can move this question if need be.
Carol

Feed two eye's worth of food

The shape of the fish tells you everything about it's insides. Of course someone who is not used to looking at fish innards might not see the same things, but a little common sense goes a long way. The first thing to consider is the length from it's mouth to it's anus. More distance = longer digestive track. Also, look at the width of the fish. The rounder the belly the larger the digestive system. Mouth size is another determining factor - larger mouths swallow larger foods, which means they have to have the stomach to handle it. SO, as soltarianknight said, it's different for each fish.

A great way to determine if you are overfeeding is to add MTS to your tank, since their population will explode from chronic overfeeding. Certainly the inconvenience of dealing with an over population of snails is worth knowing to what degree you are overfeeding. They will also let you know if you are underfeeding, which is a problem that is never addressed. As fish grow, they require more and more food. However, we get accustomed to feeding the same amount of food and can't always tell to what degree the fish have grown over time. If the snails become far and few between, then that means you are not feeding enough. There are countless other benefits to having the snails in the tank (sand, gravel or bare bottom), as well.


Honestly, I suspect that this eye/stomach thing stems from keeping bettas. Otherwise, are we expected to look and add up the size of all the eyes of all the fish of a community tank?? How abstract. But when you are feeding a single fish, "how much" is much more important, and the size of it's eye is something that can be fairly accurately estimated.
 

allaboutfish

Feed two eye's worth of food

The shape of the fish tells you everything about it's insides. Of course someone who is not used to looking at fish innards might not see the same things, but a little common sense goes a long way. The first thing to consider is the length from it's mouth to it's anus. More distance = longer digestive track. Also, look at the width of the fish. The rounder the belly the larger the digestive system. Mouth size is another determining factor - larger mouths swallow larger foods, which means they have to have the stomach to handle it. SO, as soltarianknight said, it's different for each fish.

A great way to determine if you are overfeeding is to add MTS to your tank, since their population will explode from chronic overfeeding. Certainly the inconvenience of dealing with an over population of snails is worth knowing to what degree you are overfeeding. They will also let you know if you are underfeeding, which is a problem that is never addressed. As fish grow, they require more and more food. However, we get accustomed to feeding the same amount of food and can't always tell to what degree the fish have grown over time. If the snails become far and few between, then that means you are not feeding enough. There are countless other benefits to having the snails in the tank (sand, gravel or bare bottom), as well.


Honestly, I suspect that this eye/stomach thing stems from keeping bettas. Otherwise, are we expected to look and add up the size of all the eyes of all the fish of a community tank?? How abstract. But when you are feeding a single fish, "how much" is much more important, and the size of it's eye is something that can be fairly accurately estimated.
now I know why I don't have as many MTS as a lot of people do I wanted to see my substrate move like some people told me theirs did. I might actually under feed, but I figure better to under feed and have a couple of fish kind of hungry than having my paramaters be all screwy.
 

Jaysee

now I know why I don't have as many MTS as a lot of people do I wanted to see my substrate move like some people told me theirs did. I might actually under feed, but I figure better to under feed and have a couple of fish kind of hungry than having my paramaters be all screwy.

Living substrate is specific to gravel - you cannot tell that the snails are moving around under the sand.

There's a lot of middle ground between keeping the fish hungry and having an impact on water quality.
 

allaboutfish

Living substrate is specific to gravel - you cannot tell that the snails are moving around under the sand.

There's a lot of middle ground between keeping the fish hungry and having an impact on water quality.
aw dang. I hate gravel. I'm gonna pm you and make sure I'm feeding enough.
 

Jaysee

aw dang. I hate gravel. I'm gonna pm you and make sure I'm feeding enough.

That's really up to you to determine. Enough is totally subjective.
 

Butterfly

aw dang. I hate gravel. I'm gonna pm you and make sure I'm feeding enough.
If your fish are active, have good color, and eat well then I would say you are doing just fine
Carol
 

Jaysee

aw dang. I hate gravel. I'm gonna pm you and make sure I'm feeding enough.

What do your snails tell you?
 

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