Hoki

Where they come from

Hoki (Macruronus novaezelandiae) are a cold-water, deep-living fish from the waters around New Zealand and southern Australia. In the wild they spend a lot of time down where its dark, cool, and there's steady current. That background matters, because they are basically the opposite of the typical reef fish most of us keep.

Setting up their tank

If you try to keep hoki like a tropical marine fish, you'll lose it fast. Think cold, oxygen-rich, high-flow, and a ton of swimming room. They are built to cruise, not hover around rockwork.

Temperature is the big hurdle. You are looking at true coldwater conditions (roughly 6-12 C / 43-54 F). That means a serious chiller, insulation, and a plan for what happens during summer or a power outage.

• Tank size: very large, long footprint. For an adult-sized fish, you're realistically in "thousands of liters" territory, not hundreds.
• Temperature: 6-12 C (43-54 F). Stability matters more than chasing a perfect number.
• Oxygen: high. Oversize your gas exchange - big sump, strong surface agitation, and consider redundant aeration.
• Flow: steady, not a sandstorm. You want the whole water column moving, not one jet blasting the fish.
• Filtration: heavy-duty mechanical plus biological with lots of turnover. These fish eat meaty foods and the waste load adds up.
• Aquascape: keep it open. Use smooth, secure structures around the edges if you want cover, but leave a runway to swim.

What to feed them

Hoki are predators that take fish and invertebrates. In captivity, they usually do best on a varied frozen meaty diet. The trick is keeping the food quality high and not turning the tank into a nutrient soup.

• Staples: frozen marine fish pieces (not fatty freshwater feeders), squid, prawns/shrimp, and mixed marine carnivore blends.
• Add variety: chopped clam, mussel, krill (as a treat, not the whole diet).
• Avoid: live goldfish/rosy reds, and anything that reeks of "feeder bin". That route brings disease and nutritional issues.
• Supplements: occasional vitamin soak can help, especially if your fish gets picky.

Feeding response can be strong, and they can ram into things if they get excited. I feed smaller portions more often rather than one huge dump. It keeps water quality calmer and the fish less frantic.

How they behave and who they get along with

They are a roaming, open-water type fish. Not usually "aggressive" in the cichlid sense, but anything smaller that fits in the mouth is food, and anything that competes at feeding time can trigger rough behavior.

The biggest compatibility issue is temperature. A hoki tank is a coldwater system, so most common marine livestock is automatically out. If you mix fish at all, think similarly sized coldwater species that tolerate strong flow and meaty feeding.

• Best tankmates: honestly, none for most home setups. Single-specimen systems are the cleanest way to manage stress and feeding.
• If mixing: only with robust, cold-tolerant species of comparable size that won't be harassed or eaten.
• Skip: small fish, slow fish, and anything that needs warm reef temps.

Breeding tips

Breeding hoki in captivity is basically not a hobbyist thing. In the wild they spawn offshore and the whole life cycle involves a massive environment we just can't copy in a garage fish room.

If you ever see "captive bred" hoki being claimed in a retail context, I'd be skeptical and ask for real documentation. What you can do, though, is keep detailed notes on temperature, growth, and feeding - that kind of record keeping is the only way anyone learns anything with unusual species.

Common problems to watch for

Most issues come back to coldwater logistics and stress. A hoki that is too warm, under-oxygenated, or kept in a tank that's too small will go downhill in a way that looks mysterious until you connect the dots.

• Temperature creep: the tank slowly warms over days or weeks and the fish stops eating, breathes hard, then crashes.
• Low oxygen: rapid gilling, hanging near high-flow returns, acting "spaced out". Coldwater fish burn through oxygen fast.
• Collision injuries: scraped snout, damaged fins, cloudy eyes from spooking into glass or decor.
• Water quality swings: ammonia/nitrite after big feedings or filter disruption. Meaty diets punish weak filtration.
• Parasites and bacterial infections: often show up after transport stress or poor food quality.