Mandarin fish have always been considered to be a difficult to keep species; not only because of the type of food they eat - live food - but because of HOW they eat it. With the introduction of captive bred mandarins that eat easy-to-use prepared foods to the aquarium hobby, this knocks down the difficulty level considerably, but it also helps to have species-specific knowledge to prepare for a new pet mandarin.
Like seahorses, mandarin fish are slow, methodical eaters. Instead of chasing food like other fish do, they tend to graze constantly all day on the substrate and rockwork. If this is your first mandarin, you might think something is wrong because they don't seem to be eating as greedily as your other fish do. The mandarin might take several seconds to scrutinize a single piece of food, only to decide it isn't "quite right" and move on to the next one. Most fish gorge on food when it's available, but mandarin fish eat comparatively tiny amounts of food at each feeding. These are totally normal, natural behaviors for this species.
Tips For Feeding Captive Bred Mandarin Fish:
1. In our facilities, we turn the pumps to "feed mode" then spot feed the mandarins to be sure that the food lands near them and covers the area where they're naturally grazing the rocks and substrate. Mandarins tend to eat food off substrates rather than out of the water column. If the food is floating on the water surface, they won't notice it or eat it.
2. Food type is less important to our captive bred mandarins than food size. This species has a particularly tiny mouth in proportion to its body size. Some of their favorite foods are TDO B2 or PE hatchery diet pellets, frozen Hikari baby brine shrimp, and Easy Reefs Masstick. (To feed Masstick, stick it to a frag disc and sink it to their favorite grazing area.) On arrival, they tend to prefer these favorite foods. Over time, a mandarin can learn to accept almost any meaty food that they can fit in their mouths, and customers report that they even eat flake foods.
3. If your other fish are more boisterous eaters and getting all the mandarin food before they can eat, you can find instructions online for DIY mandarin diners. Naturally, it will take time for the mandarin to feel safe in the diner and to learn how to use it.
4. In the wild, mandarins eat constantly all day long. Like seahorses, they lack a true stomach and have a fast metabolism. Mandarins need to eat at least 3 - 5x a day in an aquarium, and newly arrived or young mandarins should be fed most often so they can gain weight after fasting during transit. Many customers employ an automatic feeder that will dispense pellets while they're at work for supplemental feedings. Be sure to position the feeder so it drops pellets in an area where the water's surface tension is being broken and the pellets can sink. Floating pellets don't do a mandarin any good.
5. Our captive bred mandarin fish do not require live foods like copepods, but they certainly like to eat them. If your tank has an abundance of live foods, you may notice that your mandarin will prefer the irresistible copepods until most have been consumed. It's still important to continue offering the prepared foods in the meantime to ensure they stay familiar with these foods and to supplement the copepods.
When Your New Pet Mandarin Arrives
Upon arrival, it's not unusual for your mandarin to be sluggish right out of the shipping box. You'll notice they go into a sleep-like state at night, as well, and it can take time for them to fully wake up each morning. We recommend putting them into an acclimation box with a small hide on arrival so they don't get swept away, lost, or bullied by the other fish. Let your mandarin rest on the first day when they arrive by keeping the tank lights off, then feed them for the first time the next morning. It's a good idea to receive your mandarin when you know you'll be home the next day so you can spot feed your new fish throughout the day.
You can let them out of the acclimation box once they're eating well and active. If your tank is on the larger side, your mandarin might "disappear" for a while until they find a comfortable territory. We have had customers with very large tanks report that they don't notice them again until weeks or even months later in some cases when the mandarin is much bigger.
If your mandarin isn't eating by the 2nd morning, please reach out to us right away. These fish are bred in captivity and raised on prepared foods. It isn't normal for them to go off their regular feeds, and appetite loss is a clear indication of stress.
Some common potential stressors are - boisterous tank mates, lack of hiding places, and water parameters which are different from what the mandarin is used to. We house and ship our mandarins in water parameters closest to natural seawater, so parameters that are different can shock the fish, even if they're still considered to be "in range." When testing your parameters, pay close attention to ammonia and pH, since low pH or trace amounts of ammonia are well-known to cause appetite loss. Of course, we're happy to help troubleshoot if you reach out to us.
Is My Mandarin Losing Weight?
Since mandarins have such a fast metabolism, they may lose a little bit of weight while fasting during shipping. That's why it's so important to make sure they are eating soon after arrival.
If you've had your mandarin for a while and are wondering if you're feeding it often enough, check the dorsal region behind the eyes. It should be rounded, not sunken in. If you notice sharp features in the dorsal region or the body, your mandarin isn't getting enough feedings. The body should be rounded and full.
This wild caught male mandarin pictured below had poor body condition and hadn't been getting regular feedings for an extended period of time.
Biota captive bred Mandarin Fish eating pellets and flake food videos: