Do Fancy Goldfish Have Almost No Stomach And Smaller Digestive Tracts Than Other Fish???

In the AquariaCentral.com forums, in a thread about a 75G goldish tank complaining about high nitrates, http://www.aquariacentral.com/forums/showthread.php?p=2429760, a "Senior Member" of the forum said they did not believe me when I told the original poster that fancy goldfish had almost no stomach and shorter digestive tracts than most other fish. 

Here's my reply...

Here's a Fancy Goldfish Necropsy (Autopsy) with many nice and juicey pictures... scroll down to picture 9 to see a close up of the stomach and intestines. This article is best viewed while eating a nice big meal. ;-)

http://thegab.org/Goldfish/goldfish-...l-anatomy.html

As you will see, if you made it down to picture 9 without hurling that nice big meal, a fancy goldfish does not have much of a stomach and it's really just an enlarged section of their digestive tract which then narrows down into the intestines. Their is no real separate stomach organ like that in most other fish. Goldfish are not the only fish with the absense of a "real" stomach.

Here's a goldfish anatomical drawing which doesn't even diagram the stomach. http://www.flippersandfins.net/Image...atomyChart.JPG

There aren't many necropsies of most other fish, that I have seen over the years, in fact, I've never seen a photographed necropsy of any other common aquarium fish online, not even bigger aquarium fish... but here are a BUNCH of diagrams showing lots of anatomical drawings of other fish showing they do in fact have clearly defined stomachs. The bottome link is a perch which is, anatomically speaking, very similar to many larger cichlids.
http://kentsimmons.uwinnipeg.ca/16cm...hAnatomy-L.jpg

http://universe-review.ca/I10-82-fish.jpg

http://oceanblue2u.com/images/tropic1.gif

http://www.infovisual.info/02/033_en.html

http://www.bildwoerterbuch.com/en/an...of-a-perch.php (this one is labeled in German, I believe, based on my two years of high school German a long time ago, but down below the image, there is a translation into English and the Magen is the Stomach)

http://www.artscape.us/aquaculture/f...sh_anatomy.jpg

Do you belive me now?

And for some comedic relief...
http://www.godlikemode.com/Goldfish-Cracker-Anatomy.jpg

If any of these links do not work at any point in the future, you can use the Internet Archive Wayback Machine (see link to my blog article about this internet tool) to find the original page and/or image.

Here is one of my posts in the forum thread, the one that led to this other "Senior Member" challenging my reply....

One way to slow down the poop rate of goldfish is to feed them more often but not as much with each feeding. Goldfish have very short digestive tracts and almost no stomach at all, so what goes in pretty much comes out the other end rather quickly.

They are BIG fish so they need lots of food which is why they will forage all the time, munch on plants, etc., but I've found that when I feed mine 3-4 smaller meals on the days when I'm home all day, the fish do not have as much visible poop... compared to how some goldfish will have 1"+ long poops coming out after they eat. This will take some experimenting on the fish keepers part as to how much to feed so that the food stays inside of them longer... and thus be processed so the fish get more nutrition from the food... instead of it being forced out the other end.

The fish don't seem to munch on the plants as much when they get feedings more often either so that's a plus. Someone mentioned floating plants and I agree that floating Anacharis will greatly help with reducing nitrates since the Ancharis will grow faster when it's floating since it's up closer to the light, it can get CO2 from the surface air and still suck up nutrients from the water. It's also harder for the fish to munch on the Anacharis when it's floating compared to when it's planted since they can't tug on it as easily... as it just moves with them. My goldfish leave my BIG crypt plant alone completely. I have to trim it back regularly or it grows to the size of a basketball or larger and doesn't leave much room for the fish to swim in the front or back... and that's with a 48" x 18" footprint.

Goldfish keepers pretty much know that the poop is often the same color as whatever they just ate, which further proves that it's not being processed much while inside the fish for a short period of time. I know the fish poop must still have a large amount of nutritional value as I've seen my Mystery Snails munching on it before... after the goldfish pigged out on some blanched Zuchini slices and the poop was pretty yellow when it came out. EWWWWW!!!... but the Mystery Snails didn't seem to mind. LOL
 
I hope this helps.
 
Lenny Vasbinder aka GoldLenny in forums