Round stingray

Where they come from

Round stingrays are coastal natives of the eastern Pacific, from central California down past Baja. You find them in shallow surf zones and sandy bays, buried with just their eyes showing. That burying habit drives almost everything about how you house them.

Setting up their tank

Think footprint, not gallons on the box. A single adult really wants something like an indoor lagoon or pond with at least a 6x4 ft open sand area, and 8x4 is much better. Height is not a priority; turning radius and uninterrupted sand are.

• Temperature: 64-72 F (18-22 C). Use a chiller if your house runs warm.
• Salinity: 1.024-1.026. pH 8.1-8.4. Alkalinity 8-10 dKH.
• Substrate: 2-3 in of sugar-fine aragonite. No crushed coral, no sharp grains.
• Aquascape: mostly open sand. If you add rock, keep it minimal, rounded, and placed on the tank bottom before sand so it cannot topple.
• Flow: moderate, broad, and well-oxygenated. Avoid narrow jets that blast the sand.
• Filtration: big skimmer, oversized biological media, and a sump you can easily service. These fish are messy eaters.
• Cover: tight lid or net top. They can push up and splash.
• Intakes: guard every pump and overflow with foam or mesh so a buried ray cannot get pinned.

Rinse the sand thoroughly before it goes in. I like to add it wet to cut down dust. After it settles, run the tank a few days and gently vacuum the top half inch during water changes so detritus does not build up where they bury.

What to feed them

They eat crustaceans and small fish in the wild. In a tank, think meaty marine foods offered on the sand so they can locate it with their electroreceptors. Tongs are your friend. A ceramic feeding tile or shallow dish helps keep sand out of their mouth.

• Good staples: raw shrimp, squid, scallops, clam or mussel meat, marine fish strips (mackerel, smelt), sandworms.
• Starter live foods for new arrivals: ghost shrimp, shore crabs, or saltwater grass shrimp to trigger feeding, then switch to thawed items.
• Supplements: soak foods in a vitamin/HUFA mix; add iodine weekly to prevent goiter.

How they behave and who they get along with

Round stingrays are calm, methodical bottom cruisers that spend a lot of time buried. They will bulldoze anything loose. Not reef safe with inverts; snails, crabs, clams, and worms are snacks. Corals will get sanded over and knocked around, and the cooler water is outside typical reef ranges anyway.

• Usually fine: larger, peaceful midwater fish that ignore the bottom (lookdowns, temperate wrasses, larger gobies, some groupers if not pushy).
• Use caution: eels and big predators that might grab the disc.
• Avoid: triggers, puffers, large angels, hawkfish, and anything that nips fins. Also avoid lionfish; spines and rays are a bad combo.
• Multiple rays: only in very large lagoons. One male to two females works better than pairs. Provide lots of open space and watch for biting during courtship.

Breeding tips

They are livebearers. Mature males have claspers; females grow larger. Breeding happens seasonally in nature as temps rise in spring, with pups born late summer. It can be done in captivity, but you need public-aquarium scale space and the ability to simulate seasonal light and temperature shifts.

• Space: think 10x8 ft or bigger with gentle corners and protected pump intakes for pups.
• Cycle: a cool winter period around 62-65 F, then gradually back up to 68-72 F by spring.
• Diet: heavy on shellfish and varied seafood with vitamins to support gestation.
• Gestation: roughly a few months; litters are small. Newborns take enriched mysis, finely chopped shrimp, and small pieces of clam.
• Separate if needed: an aggressive male may harass a female. Have a divider or second pond ready.

Common problems to watch for

• Disc abrasions: caused by rough substrate or rock. Switch to finer sand, remove sharp decor, and keep water pristine to prevent infection.
• Refusing food: new arrivals often need live ghost shrimp to start. Check temperature and oxygen, reduce activity around the tank, and try feeding at dusk.
• Goiter (neck swelling): usually iodine deficiency. Add iodine and use vitamin-soaked foods.
• Heat stress: above mid-70s they get lethargic and breathe fast. Use a chiller and keep a stable range.
• Ammonia/nitrite sensitivity: rays are unforgiving of spikes. Seed bio media well and add livestock slowly. Aim for ammonia/nitrite 0, nitrate under 20-30 ppm.
• Parasites: look for flashing or excess mucus. Do not use copper. Work with a vet on praziquantel or freshwater dips only if appropriate and brief.
• Stray voltage: can make them skittish. Check equipment and use a grounding probe if needed.