Often a new arrival will not eat within the first 48 hours of receipt. Normally, your fish will resume eating when it has adjusted to its new surroundings and is once again comfortable. But occasionally you will come across a specimen that is stubborn and will refuse to eat, although otherwise healthy. Why then, is it not eating? The three most common causes are stress, parasites, and constipation.
Often transit is difficult on the animal, and acclimation to aquarium life is made doubly hard when introduced to a tank with preexisting tankmates. Be sure to quarantine animals prior to addition to your tank. This allows them ample time in solitude so that they may adjust to aquarium life. Once the animal is comfortable, they will often begin eating with gusto.
When quarantining tangs and other large fish, make sure that the quarantine tank is of adequate size. They will often pace nervously in a smaller tank, and never feel comfortable enough to eat. Use black construction paper or spray paint, and blacken out three sides of the quarantine tank before adding the animal. Black walls and dim lights tend to keep tangs calmer.
Administration of methylene blue while in quarantine or in a dip, can also help to reduce stress and speed recovery of new arrivals. Methylene blue acts as a mild antibacterial and anti fungal, while increasing available oxygen to the animal. It can also help to ameliorate the effects of cyanide poisoning (as it does with human victims). Methylene blue is also a dye, turning the water a hazy blue. This seems also beneficial to the fish as it reduces the amount of light in the water, further calming the animal down.
Though fish may look otherwise healthy, they may often come with parasites that are unseen or undetectable by us. These parasites can cause stress, thus decreasing the animalâ€™s appetite, or they may interrupt the GI tract, preventing the animal from digesting food. Quarantining allows for the close supervision of the animal, and administration of preventative medications, such as methylene blue, malachite green, copper, and so on.
If you believe that your fish may suffer from internal worms, preventing it from eating, praziquantel, commercially known as PraziPro, has been a useful tool for deworming. Administration through feeding or force feeding has been found to be most successful; however, it can be dosed directly to the water column.
Many times, the animal may be constipated from the transit and the ongoing stress. This constipation prevents further digestion and thus eliminating the animalâ€™s appetite. The simplest way to remedy this is to administer a freshwater dip. Prepare a few gallons of fresh water, and adjust it so that it matches your quarantine tankâ€™s temperature and pH. To adjust pH, you can use simple pH buffers such as SeaChem Marine Buffer, or Kent Marine pH Buffer. Many animals will defecate within seconds of being in the fresh water. Examine the feces under a magnifying glass for flukes or worms. You may dip the animal anywhere from 2 minutes to 20 minutes. Keep a close eye on it, and move it back into the quarantine tank at the first sign of distress. Often, the animal will begin eating within hours of reintroduction to the tank.
Other Ways to Convince Your Animals to Eat
If your animal is still stubborn, there are many other small tricks to get them to eat. For planktavores, an offering of live foods can elicit a strong feeding response. Live brine shrimp, baby brine, and fresh water glass shrimp are usually readily available live food sources. Once the animal is eating, gutload the live food stuffs with Prazipro or other deworming medication to help further clear its GI tract.
For animals that are herbivores or must be fed palletized or dry foods, there is anecdotal evidence that soaking foods in garlic can elicit a feeding response. Soak foods in a mixture of garlic extract and marine fish vitamin supplements, and feed in small amounts. There are quite a few commercially available garlic products such as Kent Marine Garlic Extreme, SeaChem Garlic Guard, and Ecosystem Aquarium Garlic Elixir.
If All Else Fails
If all else fails, you can help nourish the animal back to health by feeding it indirectly. Helmut Debelius, in The Marine Atlas Vol 1, suggests that many fish can absorb sugars from the water column, while not actively ingesting foods. Fructose, if available at your local drugstore, is the only appropriate sugar to dose. Fructose should be dosed 5 mL to every 10 L of quarantine tank water. This allows your animal enough survive and heal during intense periods of stress and hunger. After your animal has overcome any existing infection or other issue, it will then resume eating.
Unfortunately, on occasion, an animal will wither away despite your best efforts. Some ailments are very difficult to diagnose and treat. In this event, consider euthanizing the animal to avoid further suffering.
Take your time, and be patient with new arrivals. Follow through with your treatment regiments, and reduce stress on your animals at all costs. Usually the shyest eater will eat with gusto if treated properly.