Spotfin cardinal

Where they come from

Spotfin cardinals (Jaydia queketti) are an Indo-Pacific fish. You will usually see them coming out of places with lots of cover - reef edges, rubble, rocky areas - where they can hang in the shadows and pick food out of the water column. That whole "hover near structure" thing is basically their personality in a nutshell.

Setting up their tank

I treat these like a shy, easily-stressed fish that also wants clean, oxygen-rich water. If you try to do them in a bare, bright show tank, they often just fade out on you over time. Give them a setup where they can relax and you will see much better feeding and color.

• Tank size: 30+ gallons for one, 55+ if you want a small group (and you should, if you have the room).
• Aquascape: lots of caves, overhangs, and branching rockwork. They like "roof" cover more than just a few rocks on sand.
• Lighting: they handle reef lighting, but give them shaded zones. Floating macro or overhangs help a ton.
• Flow: moderate. Too much blasting current makes them hide and burn calories.
• Filtration: strong biofiltration and a skimmer if you can. They are not messy like triggers, but they do best in stable, clean water.
• Parameters: reef range is fine - think 1.025-ish salinity, stable temp in the mid-to-high 70s F, and low nitrate.

If you are buying one, I really like to see it eating at the store. Ask for frozen mysis or brine. A Spotfin that ignores food and just hovers with clamped fins is a gamble.

What to feed them

Once they are eating, they are not picky. The challenge is the first week or two. They can be slow and polite at feeding time, so if you have fast pigs in the tank, the cardinal ends up hungry even though you are feeding plenty.

• Best staples: frozen mysis, finely chopped shrimp, calanus, enriched brine (as a helper food, not the main diet).
• Pellets: some take small sinking pellets, but I would not count on it right away. Train them after they are steady on frozen.
• Feeding style: small amounts 2-3 times a day at first. Target feed with a turkey baster near their hiding zone.
• Enrichment: soak frozen foods now and then with vitamins and HUFA if they came in thin.

How they behave and who they get along with

Spotfin cardinals are generally peaceful, but they are not "pushy" fish. They spend a lot of time hovering and watching, especially during the day. At dusk they get bolder. In a calmer community they can be out all the time. In a chaotic tank they turn into invisible decor.

• Good tankmates: other peaceful reef fish like gobies, blennies, smaller wrasses that are not hyper-aggressive, fairy/flasher wrasses, smaller tangs in big tanks.
• Be careful with: dottybacks, aggressive clownfish, hawkfish, big damsels, and anything that likes to bully slow eaters.
• Predators: avoid big groupers, lionfish, and large eels - they are bite-sized to the wrong roommate.
• With their own kind: can be kept in groups if the tank has lots of cover. In tight quarters you may see squabbling.

Breeding tips

They are mouthbrooders (the male holds the eggs), which is really cool to see. In a mixed reef, the usual problem is not getting them to spawn - it is raising the babies. The fry are tiny and need the right first foods.

• Pairing: easiest with a small group and let a pair form. A bonded pair will hover close together and tolerate each other in the same shelter.
• Spawning signs: the male may stop eating and get a "full mouth" look while he is holding.
• If you want to try raising fry: move the holding male to a quiet tank right before release, or collect fry after lights-out with a flashlight and a cup.
• First foods: rotifers and very small live foods are usually needed at the start. Transition to baby brine later.

Common problems to watch for

Most of the issues I have seen come down to three things: they arrive in rough shape, they do not get enough food in a busy tank, or they get pushed around until they stop showing themselves.

• Refusing food: very common on new arrivals. Try live brine to trigger feeding, then wean to mysis/calanus.
• Getting outcompeted: they eat slower. Target feed and watch the belly - you want a gently rounded look, not pinched-in.
• Hiding nonstop: usually too much light, not enough cover, or aggressive tankmates. Fix the environment, do not just wait it out.
• Disease: watch for marine ich/velvet on stressed imports. Quarantine helps a lot if you can swing it.
• Mouth damage: can happen from rough nets or banging into rock when startled. Use a container to move them instead of a net if possible.

If you give them shade, calm tankmates, and a feeding plan that actually gets food into their mouths, they can be really rewarding fish. They are one of those species where the tank has to fit the fish, not the other way around.