Goby

Where they come from

Rhinogobius flavoventris is a small stream goby from East Asia, most often collected from cool, fast-flowing creeks with rocky bottoms. Think chest-deep boulder runs, clear water, and a ton of oxygen. In the tank, you want to copy that feel more than chase a magic number.

Setting up their tank

Footprint beats height. A 24-30 inch long tank lets them stake little territories without constant fighting. I run them in a 20-long (75 liters) for a small group.

• Temperature: 18-23 C (65-73 F). Cooler end keeps color sharp and tempers aggression.
• pH: 6.8-7.6. Hardness: mid-range is fine (GH 5-12, KH 2-8).
• Flow: strong. Aim powerheads or use a spray bar so the whole tank has current without being a blender.
• Substrate: sand or fine gravel with cobbles/rounded river stones. They perch and dash, so keep it smooth.
• Hides: flat stones, small caves, stacked slate, bits of PVC elbows. Break line of sight.
• Plants: optional. Hardy, low plants (Anubias, Microsorum) tied to rocks handle flow well.
• Lid: tight fitting. They launch when startled.

I like a river-style layout: pump at one end pushing across a rock field. Pre-filter sponges on intakes save a lot of grief and baby gobies.

What to feed them

They are micro-predators that hunt the bottom. New fish often ignore flakes at first. Start with movement, then nudge them onto prepared foods.

• Go-to foods: live or frozen baby brine shrimp, daphnia, bloodworms (chopped for small fish), mosquito larvae, grindal/white worms.
• Prepared options: small sinking carnivore pellets, Repashy gel (bottom-fed), quality nano granules. Soak and drop right in front of them.
• Feeding rhythm: 1-2 modest meals a day. I do a light fasting day weekly to keep them lean and active.

How they behave and who they get along with

They are classic perch-and-pounce fish. Males square up, do side displays, and chase rivals off their chosen rock or cave. It looks dramatic, but with space and sight breaks it rarely turns ugly.

• Best social setup: 1 male with 2-3 females, or a group in a larger footprint with many hides.
• Good neighbors: hillstream loaches, danios, white cloud mountain minnows, small rasboras, Rhinogobius of different appearance (watch for cross-aggro), Amano shrimp (adults usually fine).
• Iffy neighbors: delicate shrimp like Neocaridina babies (will be snacks), very slow or long-finned fish that hang near the bottom.
• Skip: big pushy algae grazers that bulldoze caves, large cichlids, or anything that needs warm, still water.

Breeding tips

Give them caves and they will usually figure out the rest. Flat stones stacked with a finger-wide gap, small clay caves, or 1/2 inch PVC elbows work well. A male will clean a ceiling spot, invite a female, and guard the sticky eggs.

• Conditioning: cool, clean water and plenty of live/frozen food.
• Spawning trigger: small water change with slightly cooler water and a bump in flow.
• Egg care: the male fans and guards. Eggs darken and hatch in about a week at 20-22 C.

Raising the babies depends on the population. Watch the hatchlings closely:

• If they are benthic right away and can sit on surfaces, you can rear them in freshwater on newly hatched baby brine shrimp and microworms.
• If they are tiny, midwater drifters, that points to a planktonic phase. Those do better with a brackish nursery (around SG 1.005-1.010) and greenwater/rotifers for the first week or two before moving to baby brine.

Common problems to watch for

• Heat and low oxygen: panting on the substrate, dull colors, random dashes to the surface. Add surface agitation, lower temp, and increase flow.
• Internal parasites (common in wild-caught): stringy white poop, weight loss despite eating. Quarantine and treat with praziquantel or levamisole as appropriate.
• Territorial scrapes: fin nips or missing scales around caves. Add more hides and sight breaks; rebalance sex ratio if you have too many males.
• Refusing dry food: mix a few crushed pellets with frozen and target feed. They usually switch within a week.
• Jumping: startled fish will clear a gap. Keep a tight lid and block cable holes with mesh.
• Fungused eggs: first-time dads sometimes fail. Pull eggs to a small container with an airstone and a drop of methylene blue, or just let them practice on the next round.