Common river galaxias

Where they come from

Common river galaxias (Galaxias vulgaris) are a small New Zealand native, mostly from cool, fast streams with clean water and stony bottoms. Think shallow riffles, cobbles, and pockets of shade. They spend a lot of time wedged under stones and venture out more at dusk and dawn.

Setting up their tank

Set them up like a small, cold, stony stream. They are sensitive and do best in a dedicated system. A 90-120 cm (3-4 ft) long tank lets you build a flow from one end to the other. Use a tight lid - they jump.

I run a river manifold with powerheads pointing down the length of the tank, plus heavy aeration. Substrate is sand mixed with fine gravel, topped with rounded cobbles and stacked slate for crevices. Keep lighting on the dim side. Plants are optional; hardy cool-water mosses tied to rocks handle the current better than rooted plants.

• Temperature: 8-18 C. Aim for 10-15 C long term. Avoid spikes over 20 C.
• Flow: strong, laminar flow with plenty of dissolved oxygen. Think stream, not pond.
• pH: 6.6-7.6 (stable).
• Hardness: soft to moderate (2-12 dGH).
• Nitrogen waste: ammonia and nitrite at 0, keep nitrate as low as you can (ideally under 20 mg/L).
• Water changes: 30-50% weekly, pre-chilled and well-aerated.

What to feed them

They are insect pickers by nature. Mine took to live foods first, then learned to accept frozen. Dry foods are hit-or-miss and usually not worth the wait.

• Live or frozen: bloodworms, blackworms, daphnia, mosquito larvae, chopped earthworms, small crickets, flightless fruit flies.
• Occasional: small pieces of prawn, finely chopped mussel.
• Training tool: wiggle thawed foods in the current so they look alive.

How they behave and who they get along with

They are quick, curious, and a bit shy with bright lights. Expect them to hold positions in the current, then dart to grab food. In groups they settle better, but you will see some pecking order stuff, especially around the best hideouts.

• Best plan: species-only group of 4-8 in a roomy stream tank with many hiding spots.
• Possible but tricky: cold-water natives of similar size that like current (e.g., small sculpins or bullies). Only in large tanks with visual barriers.
• Avoid: goldfish, tropicals, cichlids, trout, crayfish, and shrimp. Shrimp become snacks. Bigger fish will hassle or eat them.

Breeding tips

People do breed non-migratory galaxiids in captivity, but it takes patience and seasonal cues. Sexing is subtle, so keep a group and let them pair off. Spawning tends to happen in cooler months rolling into spring as temperatures and day length rise a bit.

• Seasonal cycle: give them a few months at 8-10 C with short days, then slowly lift to 12-14 C and lengthen the photoperiod.
• Spawning sites: flat stones with narrow gaps, cobble piles, and fine gravel in brisk flow. Eggs are adhesive and often laid on the underside of stones.
• After eggs appear: move the stone to a hatching box with strong aeration and gentle current, or fence off the area. Adults will snack on eggs or fry.
• Incubation: expect a couple of weeks depending on temperature. Keep fungus off with clean water and flow, rather than heavy meds.
• Feeding fry: start with paramecia/rotifers or vinegar eels, then newly hatched brine shrimp once they can take it. Use a mature sponge filter.

Common problems to watch for

• Heat stress: rapid breathing, hanging at the surface, loss of color. Fix the temperature first, boost aeration immediately.
• Low oxygen: same symptoms as heat stress. Keep the flow high and clean gunk from pre-filters often.
• Scrapes and fungus: they wedge under rocks and can scuff themselves. White cottony patches are common after a scrape.
• Refusing food: new fish often only take live foods. Start there and transition. Check temperature and current if appetite dips.
• Parasites from wild-caught stock: flukes or internal worms. Quarantine and use gentle treatments.
• Water quality swings: they are sensitive to ammonia and nitrite. Do not overstock and keep the filter pristine.