It is perfectly possible to form and keep pairs of almost any Centropyge. There is some art in the process of forming pairs, and it is not always successful even when given perfect circumstances.
A Crash Course in Dwarf Angelfish Pairing
Let's start with the basics of Angelfish reproduction. All Centropyge are considered protogynous sequential hermaphrodites. Meaning that typically a young angelfish will first be female and later the dominant individual transitions to a male. This transformation is, for the purposes of us aquarists, one directional, Juvenile -> Female -> Male; however the
literature is quite clear that bidirectional sex-change is not only possible but has been documented on multiple occasions. The transition from female to male can be completed in as few as 60 days.
Naturally Centropyge live in Pairs or Harems, consisting of 1 Dominant Male and 1-10 Females depending on the species. The females establish a hierarchy with a dominant female and then ranked subordinate females typically based on size. When the dominant male dies the dominant female will transition and take his place. It is generally inadvisable to keep harems of Centropyge in aquariums, as in all but the largest tanks, the stack of aggression knocks off the smallest individuals until 2 remain, or at best they tend to go the way of wrasses and a suddenly subordinate females transition to males and its a fight to the death.
To successfully form a pair there are 2 options, just take a male and a female and throw them together, or add 2 females together and wait for one to transition.
How do I know if my Centropyge is a male or a female?
For at least 9 Centropyge, including the flame angels mentioned/pictured above, that is easy(ish). These Angels have permanent sexual dimorphism:
C. ferrugatus, C. flavicaudus, C. heraldi, C. interruptus, C. loriculus, C. potteri, C. resplendens, C. shepardi, and
C. tibicen. Meaning, like in the picture above these angels have some differences in appearance between males and females at all times, the exact differences vary from species to species. There are several other species which exhibit temporary sexual dimorphism during spawning and courtship, but by this point it is not super helpful, to our ends. The ideal way to form a pair is with a known female and known male. It is important that, the male be slightly larger than the female, or conflict establishing dominance can occur.
Ok, but I want a pair not on that list, how can I do that?
There are several options; the first of which I will suggest is somewhat unconventional, simply buy them. There is a considerable degree of luck and "secret sauce" to forming centropyge pairs, this is heightened for the non dimorphic species. There are people out there who have already had the resources to learn and make mistakes on someone else's dime. Divers Den, TSM, PIA, Marine Collectors, all offer bonded angel pairs, and many local retailers have some guy on staff who knows how to do it. These people likely have better access to ordering and can simply get enough of one species to find a pair that work out. Fish stores and online retailers are better equipped to pair, observe, separate, and try a different individual, and should they not be able to intervene fast enough wholesale costs are lower to replace the lost individual than at retail.
Otherwise there are 2 schools of thought on pairing non-dimorphic (or all) angels: 2 juveniles, vs 1 small & 1 medium. The 2 juveniles/smalls school of thought suggests that you are trying to maximize chance of 2 females, or minimize the chance of 2 males. By selecting species which have a visually distinguished juvenile stage (
i.e. C. flavissima, P. multifasciata), or going small (<2") you can virtually eliminate any chance of getting a male. Also, anecdotally small dwarf angels tend to be more tolerant. The downside is at this size Centropyge can be difficult to keep alive, and for breeders, they may need to wait years for them to begin successfully spawning. The 1 small 1 medium has a higher chance of getting 2 males however has some advantages. The larger angels tend to have better survivability. It keeps the size delta such that one individual is not so large it easily or quickly kills the other as often happens with the "1 microscopically tiny and 1 huge" suggested; it is definitely not a safe idea to put together a huge angelfish with a tiny angelfish. It is debated over if the small+medium is overall faster or simply faster to get to spawning, by the nature of the more mature fish. Proponents of small+medium, suggest that it may be more easy to see aggression, and that there is a lot lower chance of having smooth sailing for a few months and then suddenly two fish that hate each-other, which, from time to time happens with 2 equally sized juveniles. Each option has its downsides, and upsides.
So now I have selected my potential pair what do I do with them? I think it is best to introduce them simultaneously to a completely new environment for the both of them. This is the method that I have had the most success with, though other schools of thought exist. It is ideal for them to be introduced in as large a tank as possible with lots of cover. Some times when placed, into too small a tank, or a tank without enough cover, the pair will only fight. I have had the most success in 125g, 75g, and 65g; I have had issues with very small angels in 20g longs. Once together the pair needs very close observation. Watching for signs of aggression, there will be lots of displays and chasing, but there should not be cornering nor fin damage. Aggression should be decreasing not increasing. If you see something concerning separate the fish, things can go south fast. It also can be helpful to not have any distracting fish in the tank with them, the presence of another angel or a tang can disrupt the pairing process. Though sometimes the introduction of a tang or an angel from another species can help instigate two tolerant individuals to pair, this is an advanced technique and requires special caution. It is imperative to still follow best practice, keep the water quality high, stable parameters, established tank, and feed heavy.
With luck, great suppliers, careful preparation and practice, we can keep pairs of any Centropyge!
