Tube Feeding Techniques for Fish
Syringe with catheter attached.
Here is an all too familiar scenario: an aquarist faced with trying to care for a new, expensive fish that tragically refuses to accept any food. Common sense dictates that fish need food in order to survive. The frustrated aquarist may try different foods, (“It just must not like what I’m offering it!”). They may add various “food attractants” that rarely work. The aquarist may play the waiting game, “It will begin eating when it gets hungry enough, and so I’ll just keep trying.” Many aquarists deny there even is a problem, (“I haven’t seen it eat for six weeks, but it must be eating something – probably when I’m just not looking.”). Most of this is wishful thinking – a fish that doesn’t actively pursue and consume the food you offer it is going to have a problem surviving in your aquarium for the long term.
To determine exactly why a particular fish isn’t feeding, a bit of analytical work is in order. Anorexia (lack of feeding response) in fish can stem from a variety of causes, and thus has many potential solutions – with only one best solution for each case. In addition, there are some causes of anorexia in captive fish that have no reasonable solution, and therefore are hopeless:
1) Is this species of fish known to be a poor feeder in captivity? If it is one of the “impossible to feed” species – it may never begin feeding on its own and tube feeding it will only prolong its life, not allow it to thrive and grow.
2) Has this individual fish fed well in captivity in the past? If it has fed before, what has changed to make it stop feeding? Tube feeding should only be considered in this case if rectifying the problem will take more than a week, otherwise it is usually better to simply let the animal fast until you fix the problem and it begins feeding on its own again.
3) If the animal is suffering from a disease, is the prognosis good enough to consider tube feeding it during the treatment?
4) Does the animal require a treatment with a medication that cannot be administered except by tube feeding?
Force feeding or tube feeding are both terms that describe an attempt to give sustenance to an animal that refuses to accept food on its own accord. How long can a fish go without food and still survive? Some larval fish at critical stages of their development may starve to death in less than a day if the proper food is not made available to them. At the other end of the spectrum are cases where moray eels have gone on self-imposed fasts lasting as long as 8 months, and then spontaneously began to feed again. A large saddleback butterflyfish refused all food for over 120 days and when it finally began to feed on standard aquarium fare, it didn’t look any thinner than the day it arrived from the collector. One ailing pinecone fish stopped feeding, but otherwise looked very healthy. When it finally died 6 months later, during necropsy it was noted that its body cavity was still filled with quite a large amount of fat deposits. Generally, unless there is some underlying acute disease or water quality problem, otherwise healthy fish can undergo long periods of fasting and still survive – if the cause of their anorexia is eventually resolved.
The food recipe used in tube feeding changes little from fish to fish. The basic premise is to prepare a food that is liquid enough to easily pass through the feeding syringe and tube, but thick enough to carry a high number of calories to the animal’s digestive track with the least amount of water. Avoid trying to mix a “super food” chock full of extra minerals, vitamins, fats and protein – stick to a mixture that is similar to the animal’s normal diet. Regular aquarium flake food blended with an appropriate amount of water suffices in most instances. The amount of food to administer is difficult to judge, but generally, an amount on the order of 2 to 4% of the animal’s body weight is sufficient. This should be just enough food to cause a slight distension of the animal’s belly. Too much food will usually result in regurgitation – often nearly the entire amount that was fed. Don’t be too concerned about the sterility of the food mixture or the feeding equipment – fish always ingest some tank water when they feed normally, and this obviously isn’t sterile. The food should be freshly made and the equipment washed well between uses, but sterilization isn’t necessary.
Tube-feeding equipment varies depending on the size of the fish being fed, but normally consists of a syringe and a flexible plastic tube. Feline urinary catheters or avian tracheal tubes can be used for small fishes. Larger fishes can be fed using airline tubing or horse catheters. Many prefer to use a Luer-lock syringe so the tube is held more securely to the syringe body, but the tubing can also be glued to the syringe with cyanoacrylate glue (Noga 2000). The tubing needs to be rigid enough to pass into the fish’s stomach but soft enough not to injure the lining of the gastrointestinal tract (Noga 2000). It helps with insertion if you first bevel the end of the tube. The tube must also have marks on it at regular intervals so that you can more easily judge the depth of insertion.
The actual tube-feeding technique used is difficult to describe, and a person’s first few attempts are sometimes met with failure regardless of the instruction given. In most cases, the use of an anesthetic such as MS-222 is required to quiet the fish so the tube can be inserted. In some cases, the fish can be manually restrained for the few seconds it takes to administer the food. It is generally best to first hold the tube alongside the fish’s body and mark the length needed to reach the center of the animal’s stomach. Holding the fish on its back, gently insert the tube into its mouth and try to locate the esophagus. If you are too far to the left or right, the tube will usually emerge from one of the opercula. If you have the tube positioned too high or low, it will often hang up on the tongue or vomer teeth in the roof of the mouth. Once the esophagus is located, gentle pressure is all that is needed to insert the tube down into the stomach. At that point, gently press on the syringe plunger and inject the food into the fish’s stomach. Gently withdraw the feeding tube and return the animal to a recovery tank. Keeping the animal submerged during the procedure and at all times afterwards minimizes torsion on the stomach and will reduce the chance of spontaneous regurgitation. The frequency of administering this procedure is a compromise between getting enough food into the animal while reducing the stress inherent with tube feeding. For example, a small marine angelfish might normally be fed two or three times per day, but tube feeding an animal that often is likely to cause chronic injuries that negate the benefit of the food being given. Furthermore, fish that have just recently been tube-fed are not likely to begin feeding on their own. Therefore, it is best to tube-feed small fish every second or even every third day, and always try to entice the animal to feed on its own just prior to each procedure. Some large predatory fish may only need to be tube fed once a week or so.
The following case histories will help describe some common scenarios where tube feeding has been used, showing cases that did and did not have a successful outcome.
Pinnatus batfish: Perhaps the first time this species of fish had ever been tube fed, this case was unique enough to be written up in an aquarium magazine (Hemdal 1985, 1997). In this instance, the animal eventually perished due to secondary infection apparently caused by handling during the feeding procedure. Still, the animal was kept alive long enough to actually show some growth derived solely on the food energy it was gaining by being tube fed, and it did eventually begin to feed a bit on its own.
Butterfly ray: As an aquarist for a major public aquarium, I had ordered one of these fish from a collector. Upon its arrival, my curator commented, “Too bad you didn’t ask me before ordering this fish – they always starve to death in captivity”. Wanting to prove that I didn’t make a mistake in ordering the fish, I began a three times per week tube feeding regimen for it. The animal actually began to grow as I kept up the procedure for two months. Ultimately, I became too comfortable with the procedure, and I was careless one time and inadvertently ruptured the animal’s stomach by inserting the feeding tube too far and it subsequently died of an infection.
Walking batfish: A group of these fish arrived from a collector and soon began feeding well on live mysids and brine shrimp. Previous experience with these fish told us that they are often severely infected with internal worm parasites. Our most common means of feeding anti-helminthics (de-wormers) was via medication added to gelatin food. As these fish wouldn’t eat that food, they were force fed a liquid food with an appropriate amount of Panacur added. The next day, all the fish were seen expelling dead worms from their vents and went on to be healthy aquarium inhabitants.
Garden eels: Apparently, due frequently being collected with chemicals, these fish often refuse to feed in captivity. In some cases, tube feeding them for a few weeks will keep them alive long enough that they will begin feeding on their own. The primary problem with tube feeding these fish is that you must use MS-222 to anesthetize the fish each in order to get it out of its sand burrow. Eels that are too weak to create a burrow generally do not survive no matter what you do for them.
Talma butterflyfish: This case was interesting in that the animal did not feed when it was first acquired, but soon began feeding on its own once it had been tube fed a couple of times. It then lived problem free for almost a year, and then suddenly for no apparent reason, stopped feeding. It was tube fed three times a week for two months, but never began feeding on its own again and was eventually euthanized.
Weedy scorpionfish: This animal had refused all food for 6 weeks after its arrival. After tube feeding it once it began feeding on live fish the next day and was soon converted over to sliced seafoods. This case was special in that the species is venomous so great care had to be taken during the procedure so that nobody got stung. For safety of the aquarist, the use of MS-222 anesthetic would be mandatory in cases like this.
Weedy seadragon: A very rare and valuable fish, this animal had been in captivity for two years when it suddenly stopped feeding on live mysid shrimp (the only food it would accept). It refused food for a month while it was treated with various anti-protozoan medications. It began feeding on its own for two days, and then stopped feeding again. This time it was suspected that the animal had developed a secondary bacterial infection. It was tube fed using a very tiny catheter during the four weeks it was given antibiotic injections. No anesthetic was needed, but inserting the tube through the animal’s long narrow snout was very difficult. About a week after the last injection, the seadragon began feeding on its own and has done well since then.
Force-feeding is a technique that can be employed on larger carnivorous fishes. A sedated fish is held on its back while its mouth is opened, and a food item of appropriate size for the animal is then placed in the back of the animal’s throat. A finger or semi-rigid tube is then used to gently push the food item into the stomach. In some species, such as anglerfish and eels, there are back-curved vomerine teeth in the throat that will actually grasp the food item and keep the fish from voluntarily regurgitating it. Be cautious in directly handling a fish during either of these two techniques, as some have very sharp teeth and, of course, some fish have venomous spines.
What are the drawbacks to this procedure? One problem is that until one develops a practiced technique, improperly tube feeding a fish may cause serious damage to the animal’s digestive system, or at the very least, will prove ineffectual at providing any sustenance for the animal. One can describe all the equipment, the food recipes, and when you should or should not attempt this procedure – but your results hinge entirely on how well you are able to carry out the process. This is akin to why some doctors, despite their similar training become surgeons while others prefer general practice. Remember, “Practice make better.” Perhaps the greatest cause of failure with this technique is picking a fish with an “impossible” prognosis: An animal that is dying from an unresolved protozoan disease is not going to be helped by a tube-feeding procedure. A fish that is within days of death from starvation is also not a good candidate for this technique. Knowing which fish to give up on, and which may actually benefit from tube feeding is of paramount importance to the aquarist.
Hemdal, J.F. 1997. The red-rimmed batfish - revisited. Aquarium Frontiers On-Line September 1997 http://www.petchannel.com/aqfm/1997/sep/features/1/index.htm
—— 1985. The pinnatus batfish: force feeding. Freshwater and Marine Aquarium 8(10):18.
Noga, E.J. 2000 Fish Disease Diagnosis and Treatment. Iowa State University
Press Ames Iowa