Wu's goby

Where they come from

Wu's goby (Wuhanlinigobius polylepis) is one of those niche brackish gobies that shows up from East Asia, tied to lower river and estuary habitats where fresh and salt mix. Think silty bottoms, scattered rocks, and lots of hiding spots. They are built for that in-between water and they act like it - always nosing around the bottom and claiming a little patch as "theirs."

Setting up their tank

If you want these gobies to settle in, build the tank from the bottom up. They are all about territory, cover, and a stable brackish mix. A bare "decor-only" tank usually leads to a shy fish that never really relaxes.

• Tank size: I'd treat 20 gallons as a starting point for one, larger if you want tankmates or more than one goby.
• Substrate: sand or very fine gravel. They sift and perch - sharp gravel can beat up their underside over time.
• Hardscape: piles of rounded rocks, chunks of driftwood, and tight caves. I like making several small hideouts rather than one big cave.
• Plants: go with brackish-tolerant options (or skip plants). Many fresh plants melt once you add salt.
• Flow and filtration: moderate flow with strong biofiltration. They come from oxygen-rich, moving water in a lot of locations.

For salinity, aim for a true brackish setup, not "a pinch of salt." Use a refractometer or hydrometer and mix saltwater outside the tank. I keep brackish gobies like this more stable if I pick a target specific gravity and just stick to it instead of chasing numbers.

They are also jump-prone, especially the first couple weeks. A tight lid is not optional.

What to feed them

They are bottom-feeding predators, and in my experience they do best when you feed like you would for a picky carnivore, not like a generic community fish. If you rely on flakes, you'll end up with a thin goby that hides a lot.

• Staples: frozen mysis, chopped krill, brine shrimp (as a treat), and good frozen "marine mix" type blends.
• Live foods (great for new imports): live blackworms (if you can get them), live brine, small live shrimp.
• Pellets: some learn small sinking carnivore pellets, but expect a training period. Start by mixing pellets into thawed frozen so it smells like food.
• How to feed: target feed with tongs or a turkey baster so faster fish don't steal everything.

I feed small portions once or twice a day. They will beg like they're starving, but overfeeding in brackish tanks shows up fast as algae and rising nitrate.

How they behave and who they get along with

Expect a sit-and-watch ambush vibe. They perch, dart, and then vanish back into a crevice. Once they feel safe, you will see a lot more personality: little territory patrols, head-bobbing, and short chases.

They can be pushy with other bottom fish, especially other gobies or anything that wants the same caves. With midwater fish that ignore the bottom, they are usually fine.

• Good tankmates: calm brackish fish that stay mostly midwater and aren't tiny enough to be viewed as food.
• Risky tankmates: other gobies, similar-shaped bottom dwellers, fin-nippers, and anything small enough to fit in their mouth.
• Group vs single: one per tank is simplest. Multiple can work in a large tank with lots of broken-up sightlines and duplicate hiding spots, but be ready to separate if one gets bullied.

Breeding tips

Breeding Wu's goby in home aquariums is possible in the "brackish goby" way: you need a bonded pair, the right cave, and you need to be ready for larval rearing if the fry go planktonic. Most hobbyists get stuck at the fry stage rather than the spawning stage.

• Pairing: the easiest route is raising a small group and letting a pair form, then moving the pair to their own tank.
• Spawning site: a narrow cave or tube they can guard (short PVC sections work if you hide them with rock).
• Behavior: the guarding fish will get more aggressive and may stop eating much for a bit while it watches the nest.
• Fry: be prepared for tiny foods (rotifers/microworms/baby brine depending on fry size). Many brackish goby fry need very clean water and steady salinity to make it past the first weeks.

Common problems to watch for

Most issues I see with these come down to three things: unstable salinity, rough acclimation, and not getting enough meaty food into them.

• Salinity swings: topping off with saltwater instead of freshwater (or vice versa) will mess with specific gravity. Evaporation leaves salt behind - top off with freshwater.
• Skin and gill stress after arrival: fast transfers from shop water to your tank can lead to rapid breathing, hiding, and secondary infections.
• Not eating: very common the first week. Dim the lights, add cover, and offer live or very smelly frozen foods.
• Territory stress: too few caves leads to constant chasing and fin damage.
• Parasites (wild-caught): flashing, weight loss despite eating, stringy poop. Quarantine helps a lot here.

If you get the basics right - stable brackish water, lots of bottom cover, and a meaty diet - they settle in and become a really rewarding, weird little centerpiece for a brackish tank.