Critter Goby

Where they come from

Critter Gobies are high-energy stream fish from volcanic islands in the Indo-Pacific, especially Indonesia and Papua New Guinea. Adults live in clear, fast, rocky headwaters. Their larvae drift to the sea and later come back up into the streams, so they are built for current and spotless, oxygen-rich water.

Setting up their tank

Give them a river, not a pond. A long tank with heavy flow works best. Mine are happiest in a 20-long and up, packed with smooth stones and a few calm pockets to rest in.

• Turnover: 10-20x per hour. Pair a strong canister with a powerhead or two pointed lengthwise.
• Oxygen: keep surface agitation high. Add an airstone under the flow for good measure.
• Substrate: sand or fine gravel with big smooth river rocks and cobbles. They graze those rock faces all day.
• Hardscape: stack stones to make gaps and overhangs. They like hugging the undersides.
• Plants: optional. Use tough epiphytes (Anubias, Java fern) in the slack zones. Hair algae on rocks is a bonus buffet.
• Lid: tight-fitting. They climb glass and can find the tiniest gap.
• Lighting: moderate to bright to grow biofilm on rocks.

Water numbers that have worked for me: 22-26 C (72-79 F), pH 6.8-7.6, GH 3-10, TDS 80-200. Big weekly water changes (30-50%) keep them perky.

What to feed them

They are biofilm and algae scrapers first, micro-invertebrate pickers second. If you feed only meaty stuff, they get fat-liver and fade. Keep it green-forward with small, frequent meals.

• Staples: spirulina flake, small spirulina pellets, Repashy Soilent Green/Community blends smeared on rocks.
• Grazing boosters: nori strips wrapped on a stone, blanched spinach or zucchini clipped down.
• Treats: frozen cyclops, daphnia, baby brine. Go easy on bloodworms and high-fat foods.
• Powders: shrimp baby food or algae powders dusted over rocks for juveniles.

How they behave and who they get along with

Active but not aggressive. Males posture and guard little patches of rock, mostly flaring and displaying. Chases are quick and short. Females are calmer and spend more time grazing.

• Group idea: 1 male with 2-4 females works well. Multiple males are fine if the tank is long and rockwork breaks up sightlines.
• Good neighbors: hillstream loaches, Rhinogobius-type gobies, white cloud mountain minnows, danios that like current, Caridina/Neocaridina shrimp in established tanks.
• Avoid: big cichlids, boisterous barbs, slow long-finned fish that hate current, anything that will outcompete them at feeding time.

Breeding tips

They will court and spawn in freshwater, usually under a rock ledge or inside a crevice. The catch: larvae are amphidromous. They hatch tiny and need to drift into saltwater to develop, then return to freshwater later. Getting past that stage at home is a serious project.

• Trigger: cool, fresh water changes and heavy feeding often start courtship. Males light up red and dance at cave mouths.
• Spawning site: flat stone undersides or small PVC caves facing into gentle flow.
• Raising fry: eggs hatch into pelagic larvae that need immediate transfer to marine or strong brackish water with constant greenwater and tiny live plankton (rotifers, copepod nauplii). After weeks, they can be stepped back to freshwater. Few hobbyists pull this off.

Common problems to watch for

• Starvation in new setups: a bare, sterile tank offers nothing to graze. Pre-seed rocks and feed green foods from day one.
• Low oxygen: panting, hanging near the outflow, reduced color. Turn up surface agitation or add air.
• Overheating: they crash fast in hot, still water. Keep temps in the mid-70s F and flow strong.
• Medication sensitivity: go light and add extra aeration during treatments. Test a half-dose first if the med allows.
• Jumping and climbing: they can scale silicone seams. Block every gap around hoses and cables.
• Rich, meaty diets: leads to bloat and lethargy. Keep a plant-based backbone and use meaty foods as accents.