Monthly Archives: July 2012

The Goldfish Digestive System

Jennie Connelly

The digestive tract of the goldfish is interesting because it completely lacks a stomach.  This means that food moves through the goldfish system faster than it does in animals with a stomach, because there is no space for large amounts of food to be stored.  It also means the intestines are broken up into discrete areas which  perform the different functions that a stomach normally would.  The entire digestive tract of a goldfish is quite long, typically twice the body length (McVay 1940), and is broken up into parts which form various specific functions.

The Mouth, Pharynx, and Esophagus
Food first enters the goldfish system by the mouth.  The goldfish opens its mouth to create suction,drawing food items along with water, into its mouth.  The water isexpelled through the gills, and the food items are retained in themouth. The food items then enter the pharynx, located at the very backof the mouth.  There are taste buds in the pharynx, along with teeth(called pharyngeal teeth), which grind against a hard chewing surface to break the food items down into small pieces that can pass through thenarrow intestines.  There are typically 4 teeth on each side of the pharynx; each tooth having a small immature tooth at the base, in preparation to replace the mature tooth when it falls out (McVay 1940).  After the food items have been chewed by the pharyngeal teeth, they go through a very short esophagus and enter the intestinal bulb.
Click for Photos of Goldfish Teeth

The Intestinal Bulb
Goldfish intestines can be divided into two basic parts; the intestinal bulb/midgut, and the caudal intestine/hindgut. The function of the intestinal bulb portion is to provide temporary storage of food items and to absorb lipids from the food items as they pass through the system (Caceci 1984).  The intestinal bulb is capable of expansion for temporary storage of food items, and has been observed expanded up to 3 times its normal size in goldfish examined immediately after feeding (McVay 1940).

The Caudal Intestine
The caudal intestine is the last portion of the goldfish digestive system.  It is much narrower in diameter than the intestinal bulb portion, and does not have the expanding capabilities of the intestinal bulb (McVay 1940).  The function of the caudal intestine is to absorb protein from the food items as they pass through (Caceci 1984).

Knowing more about the goldfish digestive system can help hobbyists choose foods that are better-suited to the needs of their fish.  It has been suggested that because of their relatively fast-moving digestive system, goldfish should be fed foods which can be quickly and easily digested.  Because goldfish lack a stomach, and thus are only capable of very short-term food storage and only in small food quantities, it has also been suggested that they should be fed multiple small meals throughout the day rather than one large meal.  One large meal per day could potentially overload their digestive system and cause the food items to become impacted inside the intestines.  


McVay, Jean A. and Helen W. Kaan. 1940. THE DIGESTIVE TRACT OF CARASSIUS AURATUS. The Biological Bulletin. 78:1:53-67.

How To Take Good Photos Of Your Fish

A question I see often is “How can I take better photos of my fish?”.  So here’s a collection of pointers that I’ve found helpful in getting those super-clear, high-quality photos of fish.  

1. Ambient Lighting
One of the biggest mistakes people make is to take photos during the daytime, which almost always results in ugly reflections on the tank glass.  The best time to photograph your fish is in the evening when it’s dark outside.  It’s also wise to close all the curtains and turn off every light source around you except for the aquarium light fixture.  This way you won’t get any ugly glare in your photos. 

2. Over-tank Lighting
After you have gotten all other sources of light extinguished, it’s important that your over-tank lighting is as bright as possible.  If possible, add a second light fixture on top of your tank.  In a pinch you can even drag over a floor or desk lamp and position it directly over the top of your tank.  Anything you can do to add extra light directly above the tank and shining down will improve the clarity of your photos.  Photos taken under insufficient lighting tend to be more blurry.

3. Macro Setting
You don’t need a super high-tech expensive camera to get decent photos.  But the camera you use does need to have a good macro setting.  This means that it can take very detailed close-up photos.  The macro setting is usually indicated by a little flower icon.

4. No Flash
Using flash can make your photos look harsh and cheap because they don’t allow the natural shadows on the fish to show.  Instead, they highlight the entire fish (making it appear flattened) and create unnatural shadows in the background.  Using flash also creates glare on the glass, which is something you’re already trying to avoid!

 5. Take LOTS of Photos
Good photographers take hundreds of photos just to get a few truly nice shots.  Be prepared to spend a lot of time taking photos, only to throw out most of them and have a few really nice ones when it’s all said and done.  Good photography is just as much chance and luck as it is skill.  You need to be ready to capture that picture-perfect moment when it happens, because your fish won’t pose on-cue!  You can better your chances of getting that perfect photo by taking many photos and throwing out the bad ones.  Set a high standard for yourself and keep only the best of the best.  I probably throw out about 6-8 photos for every one that I keep. 

6. A Steady Hand or a Tripod
My biggest pet peeve is a blurry photo.   If you know you don’t have a very steady hand, you can always use a tripod.  There are small inexpensive ones that can be purchased that work great.  I have one with bendy legs that can be wrapped around chairs or other objects.  I find a tripod most helpful though for full-tank photos and not as much for close-up photos, since the fish move around so much.  It can also help if your camera has an auto-timer, because it defeats the point of using a tripod if you wiggle the camera by pressing down on the button to take the photo.  You can set the auto-timer to take a photo after two-seconds, so it’s perfectly still when the photo is taken, thus reducing blur.

7. A background That Suits Your Fish 
I prefer black backgrounds on a goldfish tank, but you have to think about what background color works best for your fish.  Obviously if you have mostly black fish, it will be tough to get good shots of them if you also have a black background.  However, I’ve found that most other colors of fish do photograph really well on a black background.  For black fish, I like a light brown or light gray background.  Many people choose blue backgrounds for their goldfish because the blue compliments the orange/red colors found in many goldfish.  The background you choose will be dependent on the colors of your fish. 

8. Shutter Speed
Using a fast shutter speed will reduce the amount of light that the camera “sees”, and so will produce less blurry photos.

9. A Photo-editing Program
Once you have done all the above steps and gotten a few really good shots, a photo-editing program can make them even better.  Say, for example, you have a really clear shot of a fish in a unique pose, but the photo is crooked.  Editing software can help you fix this and other small flaws to make your photos even better.  You don’t even need to use something like Photoshop, there are free photo-editing programs out there that work just fine for most minor fixes.  One example is Windows Live Photo Gallery.

10. Practice!
If you want to get better at photographing your fish, the best thing to do is practice!  Along the way, you’ll learn new tips and tricks that work well for you and your photos will continue to improve.  Good luck!

Solid Gold on Twitter and Facebook!

Yep, you can now follow Solid Gold on Twitter and Facebook!  There have been a lot of times when I had a single photo or something I wanted to share, but it seemed silly making a whole new blog post just to share it.  So things like that will now be shared on my Twitter page!

On my Facebook page you can see albums of all the fish I have had over the years, the evolution of my aquariums over the years, and other good stuff.  🙂 

Solid Gold on Twitter

Solid Gold on Facebook

For example…

Once Upon a Water Change…

I tested the parameters beforehand.  Nitrates were at ten, and I don’t like them getting any higher than that, so it was time for a water change!

Here at our new house, the water pressure from the sink is really good.  I’m thankful for that because it makes the water changes go faster, but at the same time, it splashes water all over the place!

Nothing to see here folks, I’m just flooding my kitchen counter is all…

The tank mid-water change.  I’ve started using a little clamp to hold the python hose in place, and it works great!

Callisto checking out the stream of fresh water.  What a goof!

Update Time!

I’m sorry it’s been so long since I’ve updated this goldfish blog!  In the last couple months I moved to a new house and got a doberman puppy, so things have been a bit hectic and I haven’t been able to spend much time on my goldfish hobby.

Before the move, I had a sudden outbreak of something either parasitic or bacterial (never found out what it was) in my tank, and sadly I had a few fish losses.  I am now down to only two fish, Clover the ryukin and Callisto the broadtail.  On the bright side, having just two fish made transporting them to my new house easier, and it certainly makes caring for them easier now that I also have an energetic puppy to deal with.  I will probably get more fish sometime in the future, but for now I’m happy with just the two I have.  They have plenty of space all to themselves in my 75 gallon tank! 

Here are some photos of them from today.

Clover has developed some orange color at the top of his dorsal fin.

~dancing~  Or so it would seem!

Ever so photogenic.

Callisto was not in a cooperative mood for photos (as usual!), so just one of her.

The duo together.

 And here’s a video of them as well!