How Carp Eat 101 - Another Study Group Thread

[Carl]

I guess the Feb/Mar 08 Koi Nations may be my favorite so far because of the depth of information provided in many of the articles in that particular edition.

There was an article entitled "Chewing the Fat, Using Science to Determine How Koi Eat," by Jasper Kuijper that I found very interesting. Have you read it? If you have not I really recommend that you do.

The article starts out talking about how the food that we feed our koi can effect water quality and how important it is that our fish like the food we feed them so that they don't spit it out. The article also discusses other things such as the size and composition of the pellets and goes into some detail about the actual mechanics that a koi goes thru to process its food. Do we really need to know how our koi process their food? Probably not, but knowing that may help us better select food for our koi and make maintaining water quality a little easier.

[DebbieKSW]

I know someone that taste tests their koi food.

sounds like a good article.

[Carl]

Jasper suggests that we should choose food for our koi that does not release its protein too quickly and that keeps their vitamins well bonded. He also supports the generally accepted view that it is best if the koi eat the food as quickly as possible to minimize the leaching of protein and vitamins into the water.

According to Jasper, when the food releases its protein, it will create a film on the surface of the water. The release of vitamins will cause a discoloration of the water. Jasper suggests that we test our food by putting some pellets in a glass of water for an hour and and see how much the color of the water has changed. According to Jasper, if we use very good food, there should not be much change in the color. If we see the pellets break up after an hour, this indicates that the food is more likely to pollute our water.

How do Jasper's statements reconcile with your own experiences? Do you get an oily film on the water when you feed your fish?

Do you think the glass of water test be more informative if we tested several brands at the same time so that we could make comparisons?

[pskorf]

my thought on the 1 hour thing.
if i still have uneaten food in my pond for an hour.darn right i will have water problems;i am feeding way to much(also skimmer circuit would not be doing its job) but i would think if a koi get the pellet in the gut we need it to start breaking down.so an hour intact in pond water ,how hard is to for the koi to digest and then end up keep moving along in a short digestive track.guess that would produce excess waste also.

my thoughts

[Carl]

my thought on the 1 hour thing.
if i still have uneaten food in my pond for an hour.darn right i will have water problems;i am feeding way to much(also skimmer circuit would not be doing its job) but i would think if a koi get the pellet in the gut we need it to start breaking down.so an hour intact in pond water ,how hard is to for the koi to digest and then end up keep moving along in a short digestive track.guess that would produce excess waste also.

my thoughts

In regard to the pellet breaking down, I wonder if he is referring to the bits that pass thru the koi's gills end up floating in the water column? We may want them to stay intact long enough to be removed by the skimmer or bottom drain rather than just dissolve into the water column.

I don't know if there is a relationship or not between the amount of time it takes a pellet to dissolve in the water and how difficult it is for the koi to digest. Good point, though. Maybe someone will know the answer.

[Joey S]

My koi eat everything that hits the pond. Hardly a pellet makes it to the skimmer.

[Headache]

Carl , Great Thread Idea !

Watch your Koi eat pellets with a underwater camera . You would be surprised what comes out of the mouth & gills . If at all possible , soak your pellets in OJ (Just a little) for about 10-15 min. . This will soften the pellet and you won't see all the bits & pieces you see from a hard pellet . Also you we see your koi eat alot more food , helping to cause extra growth .

[Rick Gippner]

Even after reading this thread twice I still read the title as:

How To Eat Carp 101

Now I'll go re-read the article

[Carl]

According to a study cited by Jasper, carp can separate food from nonfood in their ingestion process. In a mud pond, for instance, they take water and mud at a particular rate so that they can just ingest the top layer of mud where most of the food is.

The koi have what's known as a palatal organ that filters the food from the mud. Who knew? These organs can "filter" from the mud "benthic invertebrates" smaller than 4% of the total length of the koi.

[Carl]

Jasper goes on to state that the physiology of the koi makes it difficult for it to eat long, plant life or struggling prey because they don't have teeth in their mouth. They have what's known as pharyngeal teeth which are located behind the gills. Apparently, food goes from the oral cavity, to the buccal cavity to the pharyngeal cavity where the palatal organ and the branchial sieve separate food from non-food. Then, the food gets chewed up before going into the esophagus.

Does that make sense? The food goes thru the branchial sieve and then gets chewed up? How does that work? When Jasper was taking about the sieve he was talking in terms of the openings being measured by microns. Was he talking about two different ways that koi eat?

[KoiValley]

Jasper goes on to state that the physiology of the koi makes it difficult for it to eat long, plant life or struggling prey because they don't have teeth in their mouth. They have what's known as pharyngeal teeth which are located behind the gills. Apparently, food goes from the oral cavity, to the buccal cavity to the pharyngeal cavity where the palatal organ and the branchial sieve separate food from non-food. Then, the food gets chewed up before going into the esophagus.

Does that make sense? The food goes thru the branchial sieve and then gets chewed up? How does that work? When Jasper was taking about the sieve he was talking in terms of the openings being measured by microns. Was he talking about two different ways that koi eat?

Sounds something like a whale doesn't it?

Karl

[Carl]

Sounds something like a whale doesn't it?

Karl

Yup. It did remind me of the whole krill sieving process that I understood some whales did.

[PapaBear]

I do think the "water jar" test has some interesting potential. Many pellets are topically treated with fish oils and vitamins to replace nutrients lost on the cooking process, but poorly prepared foods might slough off the Oils and vitamin package prematurely. The 1 hr test may not be realistic as far as how long we would see uneaten food in our ponds, but it still could serve to teach us about the relative quality of the treatment process on a particular brand.
As far as 1 hr being "too long" for a water test, at most normal feeding temperatures the food will be in the gut for 36-48 hrs and swimming in a soup of digestive enzymes the entire time. 1 hr of "non-leaching" time in pond water should not indicate slow digestion. The two environments are apples and oranges.

[Carl]

Jasper discusses two ways that koi eat food. I presume that there are only two methods, but that was not absolutely clear to me. The first method relates to how the koi eat the pellets we feed them and seems to basically involve the rounding of the mouth and sucking in of the pellet. Jasper refers to this as particulate intake and this seems to be the method with which koi keepers would be most familiar.

The second method involves what seems to be described as scooping the top layer of mud of the bottom of a pond in a fairly horizontal way. The suction is much slower than in the particulate intake method and allows for very efficient filtering which Jasper describes as moving the mud towards the sieve like organs and creating a repetitive an intake and back flow in order ingest the food matter and expel non food matter or food which is not palatable. Apparently, taste plays an important role in what get gets ingested and what gets expelled. The ability of the koi to remain horizontal while eating in this manner provides the koi with some measure of protection from predators.

[pskorf]

i do not believe a koi will keep food in their gut that long 36-48 hours is a long time.if a koi has short digestion tract that sure is a long time.

[Carl]

bump

[CHICHI]

i do not believe a koi will keep food in their gut that long 36-48 hours is a long time.if a koi has short digestion tract that sure is a long time.

This is Temperature Dependent with literature relating 16 hrs at 25C and as long a time period as up to 60 hrs at 12C

[tyco4357]

Carl , Great Thread Idea !

Watch your Koi eat pellets with a underwater camera . You would be surprised what comes out of the mouth & gills . If at all possible , soak your pellets in OJ (Just a little) for about 10-15 min. . This will soften the pellet and you won't see all the bits & pieces you see from a hard pellet . Also you we see your koi eat alot more food , helping to cause extra growth .

I like that idea alot!

[Steve Nguyen]

I read this article when it first published and have some reservations about its contents. in some of the article contents, it seems to fit under "opinion" section. no offense to the author.

when talking about digestion time, water temp plays a big part. my observations, it can take couple hours to digest at warming water temp vs long period during cold water temp such as mid 40 F degrees. one thing for sure, pre-soaked pellets digest faster and less waste.

speaking of leach out nutrients, if took almost 30 mins to soften pellets if pre-soak with lot of water and soaked pellets will re-absorbed all liquid back into the moist pellets so not sure about how much nutrients will end up losing. furthermore, if pre-soak for 15 mins, there is still hardness inside the pellets thus not all nutrients leach out as some might claimed. my observation was that my fish feed much more agressive with moist pellets and grow much faster too.

Steve

[koiman1950]

Well, this article deals with TWO distinct feeding habits. In our concrete pond environment, I really think we only deal with one - particulate matter feeding. Based on a few observations over the years with various food brands, I found a few that are very oily in content and do leave a film on the surface of the water, including Saki Hikari. So, although many like the quality of this food, I stopped feeding it in 2007 and went back to OSI/HiSilk mix during summer of '08. I will say I notice a small difference in amount of waste produced between the two, but the trade off is the oily slick produced which, to me, goes directly to adding to DOCs and increased foam production. I've never actually tried soaking my pellets. If anything, I would make a paste food and rather than mixing with water, I would use either orange or cranberry juice. I would think that the least amount of water used to soak pellets would be the most beneficial with regards to what Steve mentioned about the absorption of moisture by the pellets. I would think in this issue, less is more. I watched Sakai feed his fish while on a visit there in January of '07, and he used a small amount of water to soften the pellets. Of note here, I only saw ONE TYPE of formula pellet on the premises and there were at least 25 or more 20 or 25 kilo bags stacked up. No difference in protein levels or any of that other stuff we seem to be consumed about when feeding in Spring/Summer/Fall! I still believe in changing the amount of food but not the protein levels. OSI is fed all year, here, and HiSilk is added in Summer.

Mike