My New Fish Won't Eat! Tips


Well-Known Member


This phrase is heard much too often. I understand hobbyists that by online fishes and receiving them only to find out they are not eating (despite promises from the shipper/supplier). I understand people who buy marine fishes that were told the fish was eating. But I find it hard to understand why they didn't ask to see the fish eat before they acquired it.

Buy fish from your LFS. Watch the fish being fed. Even an LFS employee or owner with good intentions could have ‘thought’ the fish was eating. They can’t be expected to remember whether every fish is eating. Yes, they could be lying, but I’ll give them the benefit of the doubt under most circumstances. One of my LFSs always says, “Yes” when asked if the fish is eating. I then always ask to see it eat. So far, he is running about 10% of the Butterflyfish, Angelfish, and Tangs actually eating in front of me.

If the hobbyist, especially the new hobbyist, will just buy already eating fish, there will be much less angst for the beginner. Buying marine fish is not to be done emotionally or taken lightly. It is a life you have agreed to care for for the rest of its life.

If living someplace where marine fish just aren’t available and buying online is the only option, or you have to take what you can get at your LFS, then there is some justification for having a fish in your quarantine tank that is not eating. I would only hope that you truly went the extra mile (or 50) to get to a good LFS for your fish, though. Getting fish to eat is not easy, nor is it ever guaranteed, even if the fish is ‘easy.’ Which brings me to an important point about this post. This post is for ‘easy’ and ‘moderate’ or ‘medium’ care marine fishes. If you’ve chosen to buy a fish that belongs in the ocean because it is known to be a specialized eater, or bought a fish you have been told in at least one place it is a 'difficult' or 'hard' fish or a fish that should only be kept by advanced aquarists, then you’ve wasted your time, money, and our natural resources.

If the above sounds like I’m angry or upset, then you’ve got the gist of my attitude on this subject. Hundreds of thousands (if not millions) of marine fishes die every year that never began to eat. Those who order, buy or ‘settle’ for fishes that may or may not be eating, are wasting life and our natural resources. There will never be an improvement in the capture, handling, and delivery of marine fishes for the hobby if the hobbyists continues to buy fishes that are not eating in captivity. DEMAND EATING FISHES. BUY CAPTIVE BRED FISHES WHENEVER POSSIBLE.


It is almost impossible to get a marine fish to eat without some appreciation of why it isn’t eating in the first place. Unfortunately, there are many things that can cause a marine fish to not eat. Let’s review why some fishes don’t eat.

1. Stress
This is the primary one. You may have read posts of mine responding to people asking for advice on getting their fish to eat that this is the reason why it isn’t eating. If you can remove or lessen the stress on the fish, most ‘easy’ to ‘medium’ care marine fishes will eat.

This is a list of most stressors, in no particular order, that act to deter a fish from eating:
  • Bad acclimation
  • Disease or ailment
  • Poisoned or ongoing poisoning
  • Water quality
  • Shock or inability to cope with captivity
  • Injury
  • Environment - unfriendly
  • Environment - unfamiliar
  • Held captive by King Kong
  • Digestive disorder
I don’t want to go into each on the list in depth. But something(s) about most of them is worth some mention.

Bad acclimation doesn’t just mean by the person that acquired the fish. Hopefully the hobbyist has learned enough to know the proper procedure. if not, then follow the sticky on how to acclimate fish, found in this Forum. Fish acclimation also includes people along the line, from time of capture to the person or business that you obtained the fish, who may have made an error in the handling and/or processing of the fish. The fish may not recover from this error. However, more times than not when it’s an acclimation problem, it is the hobbyist’s responsibility. This group of fishes include the deep water fishes that were not acclimated properly to surface pressures before being brought up from the depths.

Poison is a bigger topic than the reader might think. It isn’t just ammonia and nitrite, the typical waste poisons, it also is all the chemicals to which the fish may be exposed from time of capture. A wholesaler can’t sell fishes to dealers if they are dead and likewise the dealers (LFSs) can’t sell dead fish to the hobbyist. There is a drive to put medications like copper, formalin, antibiotics, off-the-shelf products, etc. into each of their systems so the fish live long enough to get to your tank. They are not being cured, just ‘holding’ from getting worse. Copper, formalin, and many meds are poisons. The hobbyist who ‘cleverly’ comes to the conclusion to treat all new fish with copper is reducing the likelihood that the new fish will eat. So the poisoning just keeps on going, down the line. Cyanide salts used to capture some fish, also fall into this category of a poisoned marine fish. So, this topic isn’t just waste ammonia and nitrites in the transport bag, but includes many others chemicals, including medications, that can act like poisons.

Water quality is something the hobbyist can control – at the time of acquisition. Combined with the Poison topic, this is a major contributing factor why fish won’t eat. Hobbyists need to expand their concept of water quality to include Poisons and the thousands of things that go untested. Many hobbyists still don’t realize that the water they use to make up their salt solution is the major cause of pollution in the marine system. Get a feel for these by reading the sticky post on water quality.

Obviously an injured fish is not likely interested in food. But there are other injuries, like to the jaw or to the long ‘nose’ (i.e. Copperband Butterflyfish) that without close inspection, would go unnoticed. These fishes can’t eat because of being physically impaired from eating, like from a mouth injury.

Environment plays a role. It can be that tank mates have made it impossible to eat. The fish learns that if it tries to eat, it will be bullied or abused. Hobbyists are not good at seeing this. Sure they can easily see a fish chasing another fish, but fishes communicate very subtly and a fish could be bullied even without the chasing and the beginner hobbyist being totally unaware. Also, the environment the fish was in, is no longer where it is now. Sort of a, “We’re not in Kansas anymore, Toto” syndrome. This effect is not shock which I define as a fish totally unaware of what is going on around it. Some beginners use this one as an excuse to bypass quarantine. However, a properly established quarantine tank does not contribute to this stress -- it reduces this stress. Read the sticky post about the quarantine process.

My favorite – The King Kong (KK) analogy. If you were captured and held captive by King Kong, how would feel every time KK looked at you? The hobbyist is the enemy/predator to the fish. One that looked just like the hobbyist snatched it from the ocean. Since then it has been netted, poured, and dumped into other containers by giants who look just like the hobbyist. Think they feel comfortable around you? You want the fish to eat, but you are standing there looking at the fish. They do know when you are looking at them – sensing being look at is one of their ‘natural alarms’ to avoid predators. This reaction has to be overcome so the fish can have confidence to eat in front of you.

Digestive disorder is more common than you might think. A fish going through the captive system that never ate since it was in the ocean, could have lost its intestinal bacteria. If intestinal worms complicate the matter, the fish may have used up all its reserves and was nearly dead when acquired.

Some from that list are not things the hobbyist can control. If you’ve ever heard the phrase, “When the fish calms down. . .” then you’ll know it is sometimes just up to the fish to cope with captivity and get on with its life. These things are for the fish to adjust and what we might chalk up to as being luck.

2. Wrong Food
Even experienced hobbyists fall into the trap of thinking, “If I can just find the right food, the fish will eat.” Not! It’s a combination of the right food and the right circumstances and the right presentation. Believe it or not, the ‘right food’ is not the most important.

There is one very important indication that the food being fed is not the right food. If the fish has acclimated and not under stress, it will 'try' to eat. If the food is taken in then spit out, the fish is showing dissatisfaction with the choice of food, (see below for reasons). A fish that takes in food and 'wags its head' is indicating that it is willing to eat, but this food is not to its liking. That doesn't mean that in a few days the fish will eat voraciously that same food it spit out; it just means that what is being fed presently doesn't tempt it much to swallow.

The hobbyist can experiment trying different foods, but has no idea what the fish was eating before it was captured. That handy paragraph in the fish book or online description lists things the fish is supposed to eat but no one told the fish that. What sometimes happens in nature is that a fish finds a food that is readily available and focuses on that particular food for its diet. For instance, stomachs of some Pufferfishes were examined to find just one kind of sponge or algae or polyp the fish liked, whereas the same fish in other locations has been dining on crab. Even though the Puffers were of the same species, they have gotten into the habit of searching for and eating a primary kind of food.

Since the newly acquired fish isn’t talking, how can we find the ‘right food?’ We can’t. It would be a huge guessing game. It would be like winning the lottery. Possible but not likely.

The second most common trap in this category is that even experienced hobbyists ‘swear’ that such-and-such food will work. It worked to get their fish to eat, so it’ll work for the next fish. Not! (again). When a fish starts to eat a food for the first time, it wasn’t primarily the food. It was just the right time for the fish to start eating. More than likely the items in 1. above were corrected and/or the fish has settled down. You may prove this to yourself. When the fish does eat, vary the foods every day and I think you’ll find it will eat other foods, too.

3. It just doesn’t look or taste right.
How important then is the choice of food. It has some importance. If you read the fish nutrition sticky post in this Forum, you’ll find that the way the food is presented can pique curiosity and/or get the fish into the mode of ‘hunting.’ This has a much greater impact than the choice of food. Living and swimming/moving foods have the greatest advantage of stimulating the hunting mode and getting a stubborn fish to eat (IF the fish eats such things). Other living foods, like corals, sponges, sessile creatures and such, are not that easy to simulate. Another reason to avoid obligate coral eating and specialized eating fishes.

Another food feature would be the way the food tastes or feels to the fish. Even though, for instance, the pod eater has been eating pods in the wild, it may find that it doesn’t care for brine shrimp (dead or alive). Switching to an actual ocean food like plankton or ocean mysis would be the optimum choice.

Some fish will seem to want to eat. They take in the food and then wag their heads and usually spit it back out (see 2. above). This fish didn't like the texture, taste, size, or any combo of these, of the food offered. It is being picky in that the food offered is unfamiliar. NOW is the time to start choosing different food and sizes because THIS SIGN from the fish is that it doesn't like the texture or taste of what is offered. These fishes are trainable to eat most foods if the hobbyist will just be patient and keep at it. Fish though that are obligate coral eaters and specialized by chance or design, will not easily be fooled into accepting prepared foods.

4. Despite what you’ve heard, size does matter.
The conundrum: The fish can most easily see a large bit of food; the fish can’t swallow what it sees. Many fish know instinctively that the size of what they are looking at is too large for them. My Chromis love to pick tiny bits of prepared foods from the water column that the other fishes in my community tank can’t even see! Yet my Copperband charges for the big chunk it easily sees, but can’t swallow. The size has to be right for the fish.


Ideally, you’ve done A. But realistically you’re reading this because your new fish won’t eat.

A. The best advice is still to acquire tank bred fish. Next is to only acquire fish you SEE eating and then buy some of that food to begin the training to eat the proper foods. Anyone telling or assuring you the fish was eating (and you failed to observe it eating or bought it online), then find out what it was eating and try the exact same food.

B. The fish won’t eat, so you embark on this journey:

The best thing is to remove and reduce the stressors on the fish that you can control. There are many more and kinds of stress that you should also become aware of if you want to keep ‘medium’ or ‘hard’ care marine fishes. Check the sticky post in this Forum on stress.

1. These stressors you can do something about:
Acclimate the fish properly.

Quarantine the fish to handle these stressors: disease, injury, tank mate issues, environment issues, and training to get to eat. A new fish in the display is pretty much ‘lost’ and will be less likely to learn to eat prepared foods as long as the surroundings match that where it got its food from (e.g., live rock) in the wild. Provide a quarantine tank (QT) with some (maybe) familiar, but artificial things. The plastic tube is okay, but how about adding some fake rock and maybe a plastic plant or too (suitable for saltwater, of course). Improving the environment from what the fish has experienced since it was captured can go a long way to helping calm the fish. QTs don't have to be boring nor totally bare. Follow the sticky post guidelines for the QT.

You need to be sure the water quality is top notch. Don't assume anything here. Check your source water (see the sticky post on water quality). Look for and reduce or eliminate sources of poisons, pollution, and control all the things you can test for. Stabilize that water once it is top quality.

If the fish is not eating after the second day, change 50% of the water, making sure to use pure source water with your artificial salt AND be sure to follow water change guidelines found in the sticky post. Sometimes a water change will correct a water quality issue. Sometimes a water change will just ‘perk up’ the fish and it will begin to eat. If it does begin to eat after the water change – change the water every other day in 50%+ increments.

If the fish is in shock then pray, burn incense and/or light candles (outside). or whatever you do when things are out of your control and you want them to improve.

For the King Kong stressor (see above) you can do something. The QT should be in a low human traffic and quiet area, but it should be somewhere the owner will spend a couple of hours each day sitting in front of the QT. It should be on a solid support and receive no vibrations but maybe from a single small air pump (the sponge filter pump). The lighting of the area (room) AND on top of the QT should be muted or low. Just enough light is needed so the fish can see the food you’re putting into the QT and enough light for the fish to be able to see you. If the hobbyist will just spend the hours in front of the QT then the fish comes to realize you are not the threat most other humans have been to it. This will help calm the fish and get used to you AND to captivity. When the fish is fed, your presence doesn’t have to be problematic to the fish – it has come to know you. This will encourage the fish to eat in front of you.

The last stressors -- digestive and intestinal problems -- are not easy or just plain not possible to address. However, be prepared to feed de-worming food JUST as soon as the fish is eating well.

Regarding the other reasons why newly acquired fish won't eat:
2. Know what to feed. Be sure you know what has been published about the diet of the fish. That is all you have to go on, so use it. Try to feed a food that matches what foods they are supposed to eat. Start with frozen. Since taste and texture is part of the equation, don’t assume that frozen brine from one company is the same as the frozen brine from another. Mix and match suppliers/manufacturers of the same kinds of food. If no luck after trying a mix of those, then go directly to live food. Any kind of food, even the wrong kind. is better than a fish that is not eating. Just be sure to quickly train the fish onto the nutritious foods given in the sticky post on fish nutrition.

3. Find a way to present the food better or more natural. You could choose to put in an opened clam or one of the miniature clams on the half shell now sold at some LFSs. You can try to push some food into a fake rock or decoration. In the case of living food, it comes with its own presentation! Live brine shrimp, and live pods are a good choice. Live small/tiny worms (Blood worms) are worthwhile too. BUT you don’t put living rock into the QT. YOU CAN catch (brine shrimp net) some of the living things off of the live rock and substrate to put into the QT. Other foods may have to float or rest on the bottom for a time for a fish to notice it, before being removed from the aquarium to limit water pollution. Some fishes do come to the surface to feed and may look up for food. Try flakes and other floating foods. Other fish look down. Try sinking pellets. If there is a current in the tank, put the food in a place where it will move – roll along the bottom or move around with the current. This adds some movement to the otherwise ‘dead’ food, which can stimulate a hunting reaction in the fish (IF the fish hunts). As soon as possible after the fish eats, get it eating the right kinds of foods.

4. I kept this part of food presentation separate since it deserves special consideration. Pay attention to the size of the food. I wouldn’t give a 6-month old human baby a steak to eat. Nor should we be offering foods that the fish can’t swallow. But even more importantly, some fish, even with large enough mouths, require small bits of food. Try different sizes, but best to find out from other hobbyists what size food their fish is eating.


These are the ‘tips’ (abbreviated by the blue highlighting) for getting a new fish to eat. Once the fish begins to eat, vary the foods daily AND train to eat the high quality prepared foods the fish should be eating, along with supplements. Be sure to read the sticky posts in this Forum for details, ideas, procedures, and fish nutrition requirements.


I hope you found the above helpful. There is no magic or special trick to get fish to eat. There is no short cut. The above listed tips cover the vast majority of why fishes don’t eat. Almost any tip you've heard about or tried, has some basis in the above list of why the fish won't eat. Getting fish to eat is simply the process to overcome those inhibiting factors. Just remember that there are some reasons and causes that we can’t solve (fish in shock, one that won’t acclimate, injury to mouth, fish caught with cyanide, fish poisoned, etc.) and the fish will continue to starve. The fish could even begin to eat and then stop for no apparent reason. If this happens, all you can do is re-check all the reasons for a fish not to eat and go through the tips again, addressing what you have control over.

For the sticky posts mentioned above, look at the top of the Forum:

Good luck!