White-edged cardinalfish
Jaydia albomarginatus
The White-edged cardinalfish exhibits a striking bluish-black body with prominent white margins along its dorsal and anal fins.
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About the White-edged cardinalfish
Jaydia albomarginatus is a small marine cardinalfish from the Western Central Pacific. Like a lot of cardinalfish it is a mouthbrooder, and FishBase notes distinct pairing during courtship and spawning - the kind of behavior thats really fun to watch when a pair settles in. Its not a big open-water swimmer, so it does best with plenty of rockwork and calmer tankmates.
Quick Facts
Size
10.2 cm SL (about 4.0 inches SL)
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
30 gallons
Lifespan
3-6 years
Origin
Western Central Pacific
Diet
Carnivore/micro-predator - small meaty foods like mysis, brine, copepods, finely chopped seafood
Water Parameters
24-28°C
8-8.4
8-12 dGH
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This species needs 24-28°C in a 30 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give them a rockwork-heavy tank with caves and overhangs - they like hanging in the shade and will look stressed if the tank is wide open and brightly lit.
- Keep marine salinity steady around 1.024-1.026 and avoid fast swings; they are way touchier about sudden changes than slightly-off numbers.
- They are dusk feeders, so toss food in after the main lights dim (or at feeding time with flow lowered) or bolder fish will steal everything before they even notice.
- Feed small meaty stuff like mysis, brine enriched, chopped shrimp, and pellets once they are trained; start with frozen and slowly mix in pellets until they take them confidently.
- They are peaceful with other calm community fish, but skip hyper bullies and fast pigs like big wrasses, dottybacks, or aggressive clowns that will outcompete them at every meal.
- If you keep more than one, add them together and give extra hiding spots; in tight quarters a dominant one can keep the timid one pinned in a corner and starving.
- Watch for mouth injuries and rapid breathing after shipping - they hide a lot anyway, so the real red flag is a fish that will not come out to eat even at lights-out.
Compatibility
Good Tankmates
- Other peaceful cardinals (Banggai or pajama cardinals) - they usually ignore each other, and they all like that calm, lower-light vibe. Add as a small group if the tank is big enough so one fish does not get picked on.
- Clownfish (ocellaris/percula) - most pairs are fine with white-edged cardinals since the cardinals just hover and mind their own business. Keep it to the more mellow clowns, not the super territorial ones in tiny tanks.
- Small, peaceful gobies (neon goby, clown goby, watchman goby) - great match because they use different real estate and do not hassle midwater fish.
- Firefish and dartfish (Nemateleotris) - similar temperament and speed. They both do best in a quiet tank with plenty of rock nooks and a lid.
- Blennies like tailspot or bicolor - generally safe since they perch and graze, and they are not interested in chasing cardinals around.
- Peaceful wrasses like possum wrasses or smaller Halichoeres (in a roomy tank) - active but usually not bullies, and they do not outcompete cardinals too badly if you feed smart (a couple small meals).
Avoid
- Dottybacks (like orchid dottyback) - they are 'small but spicy' and will absolutely punk a timid cardinalfish, especially once they claim a cave.
- Hawkfish (flame or longnose) - they sit and watch like they are innocent, then they go after small, slow fish and shrimp. Cardinals are classic targets in smaller setups.
- Big, pushy wrasses (six-line, many fairy/flasher males in tight quarters, most aggressive Halichoeres) - constant buzzing around stresses cardinals out and they can get harassed at feeding time.
- Aggressive or territorial fish like larger damsels and most pseudochromis-family bullies - if it nips, chases, or owns half the rockwork, your cardinal will just hide and slowly waste away.
Where they come from
White-edged cardinalfish (Jaydia albomarginatus) show up around reefy coastlines in the Indo-Pacific. Think rubble zones, ledges, and little shadowy pockets where they can hang back and let food drift by. In the tank they act the same way - they want cover and calm spots, not a wide-open racetrack.
Setting up their tank
If you set the tank up with places to hover and hide, these guys settle in fast. They are not a fish that appreciates being out in the open under full blast lighting with nowhere to duck into.
- Tank size: I would start at 20-30 gallons for a single or pair. For a small group, 40+ gallons gives you way fewer squabbles.
- Rockwork: Build caves and overhangs. They love a shaded nook they can claim as a "home base."
- Flow: Moderate is fine, but leave a couple of calmer pockets behind the rockwork.
- Lighting: They do fine under reef lights, but they behave more naturally with shaded areas (overhangs, branching rock, macro, etc.).
- Water: Keep it stable. Typical reef salinity (around 1.025-1.026), steady temp in the mid-70s F, and low ammonia/nitrite (zero).
Give them a "hangout corner" early. I like to place one deeper cave and one shallow ledge. They almost always pick one and you will see them relax once they have that spot.
What to feed them
They are easy once they recognize food, but some can be shy for the first week or two. Mine did best with smaller meaty foods offered a bit more often, especially early on.
- Frozen: mysis, brine (better if enriched), chopped krill, chopped clam/squid, reef blends
- Small foods: copepods, small pellets (0.5-1 mm), finely chopped seafood for smaller individuals
- Live (helpful for new/shy fish): live brine or live pods to get them eating confidently
If yours hides during feeding, use a turkey baster or pipette and gently squirt food toward their cave entrance. After a few days of that, they usually come out on their own.
Aim for 1-2 feedings a day. They are not pigs like some damsels, so if aggressive tankmates are around, you may need to target feed or feed in two spots.
How they behave and who they get along with
White-edged cardinals are generally peaceful and a little understated. They hover, they watch, and they dart out for food. The main drama is usually with their own kind if space is tight or if you try to keep an odd mix of sizes.
- Good tankmates: gobies, blennies, smaller wrasses that are not bullies, clownfish that are not hyper-territorial, peaceful reef fish in general
- Use caution with: dottybacks, larger hawkfish, big aggressive wrasses, and pushy damsels that will outcompete them at feeding time
- Avoid: predators that can fit them in their mouth (groupers, big lionfish, big hawkfish depending on size)
They can look "fine" while slowly starving in a tank full of fast eaters. Watch the belly line. If it starts looking pinched, step in with target feeding.
You can keep them singly, as a pair, or sometimes in a small group if the tank is roomy with lots of broken sight lines. If you try a group, add them at the same time and keep rockwork complex so one fish cannot patrol the whole tank.
Breeding tips
Like a lot of cardinalfish, they are mouthbrooders. If you get a compatible pair, you may see the male holding eggs in his mouth and refusing food for a while. It is cool to witness, but raising the babies is the tricky part.
- Condition the pair with a steady rotation of meaty frozen foods (and some smaller foods) before you expect any spawning behavior.
- If the male is holding, keep stress low - no chasing, no major rock rearranging, no netting.
- If you want fry, you will need a separate rearing setup and tiny foods (rotifers and/or very small live plankton). Newly released fry are not going to take crushed pellets.
Do not panic if a holding male stops eating. That is normal mouthbrooder behavior. Just keep the tank calm and let him do his thing.
Common problems to watch for
Most issues with this species are the usual reef-fish stuff, plus a couple of "cardinalfish quirks" like shyness and being slow at the dinner table.
- Not eating at first: very common. Try live foods for a few days, dim the lights at feeding, and target feed near their shelter.
- Getting bullied: they will not fight back much. If a tankmate repeatedly rushes them, you will see them stay pinned in the rocks and lose weight.
- External parasites (ich/velvet): watch for flashing, rapid breathing, and fine dusting or spots. Quarantine new arrivals if you can.
- Mouth damage: rough nets and chasing can scrape their mouth. Use a container to move them if possible.
Fast breathing and hiding in the flow can be an early sign of velvet. Do not wait it out. If multiple fish are breathing hard, move quickly with a plan (hospital tank, proven treatment, and oxygenation).
If you give them cover, keep the tank peaceful, and make sure they actually get their share of food, they are a really rewarding "quiet" fish. They do not steal the show, but they add that natural reef vibe of a fish hovering under an overhang, watching everything.
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