The Mandarinfish is one of the saltwater fish that often draws people into the hobby. This is a male, as can be seen by the first rays of the dorsal fin being much longer than the rest. While these fish have been raised in captivity and learn to feed on pellets, they are much like seahorses and need to be fed several times a day. Just dropping in pellets when you feed your other fish in a large tank is not enough since they may not get enough food or may be more interested in the live creatures crawling on the rocks. Keeping them in a smaller tank to monitor their weight is best rather than dumping them in a larger tank they can get lost in. If you have a tank with at least 100 pounds of live rock that has been well seeded, that will support one mandarin. If there are other pod eaters then you will need more live rock than 100 pounds. Avoid corals that are near the bottom and have tentacles like the Elegant Coral, since a bumbling Mandarin can easily find itself stung by that particular coral and die. This was a sad experience I personally had and will never have a Mandarin with such a coral again.
This is a great video that can identify that odd behavior your male and female mandarins may be displaying! Mandarins have been bred in captivity and trained to eat pellets. This has helped the survival rate of these beautiful fish! They cost up to 4 to 5 times more than the wild caught Mandarinfish, however, their survival rate is worth the cost!
These Scooter Blennies show that it is quite easy to have spawning in captivity. They need a lot of live food found on live rock like copepods and small amphipods. Each Scooter Blenny needs 100 pounds of live rocks that is supporting these little inverts. Tank raised Scooters will adapt to eating small pellets and should not be housed with aggressive, fast eating tank mates that will outcompete them for food. Wild caught that have plenty of live rock can be housed with such fast eaters, however. The male has a large first dorsal fin that he displays to attract his female.
Scooter Blennies, like the well known Mandarinfish are difficult and only intermediate to advanced aquarists should attempt to keep them. Unless the Scooter is eating pellets, they need a tank that has at least 100 pounds of mature, established, and copepod ridden live rock. If they are trained to eat small pellets, some aquarists will put them in a small jar that only the Scooter can fit into and eat peacefully from. Males and females are known to readily spawn in captivity if well fed.
This is a great video showing a male and female pair of Spotted Mandarinfish. The male a long first fin ray on the front of the first dorsal fin. If a pair is wild caught, 300 pounds of live rock with established copepods will keep them happy as long as there are not other fish that eat copepods in the tank. If they are a pair that was raised in captivity, a much smaller tank can be used since they are typically raised to accept pellets. The only problem is that at times if there are copepods in the tank, they have been known to favor them over the pellets. An aquarist cannot just add a tank raised Mandarinfish into a 90 gallon tank and drop in pellets and expect it to get enough to eat if there are other fish eating the pellets as well. Some have trained their mandarin to enter into a small glass container with an opening only big enough for them to enter and put pellets in the container. The fish can easily get enough to eat. They still need to be fed more than 3 times a day, similar to seahorses because these fish eat all day in the wild.