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title: "Royal Dottyback: The Complete Reef Care & Tank Mate Guide" description: "The definitive royal dottyback (Pictichromis paccagnellae) care guide: the bold purple-and-yellow reef fish, managing its aggression, pest control, royal gramma look-alike, and tank mates." slug: royal-dottyback commonName: Royal Dottyback scientificName: Pictichromis paccagnellae family: Pseudochromidae order: Perciformes difficulty: Beginner minTankSize: 30 temperature: "75–82°F (24–28°C)" ph: "8.0–8.4" hardness: "Marine — SG 1.020–1.026" lifespan: "5–7 years" maxSize: "3 inches (7 cm)" origin: "Western Pacific" publishedAt: "2026-06-05"

Royal Dottyback: The Complete Reef Care & Tank Mate Guide

The royal dottyback is a jewel with attitude — a tiny fish split sharply into electric purple and bright yellow, hardy and reef-safe and useful for controlling bristleworms, but pugnacious far beyond its size. Pictichromis paccagnellae packs the colour of a much pricier fish into a cheap, tough package, but its bold temperament means it needs careful stocking, and it's frequently confused with the gentler royal gramma — a confusion that causes real tank conflict.

This guide is the complete reference: royal dottyback biology, managing its aggression, its pest-control value, the gramma look-alike issue, and tank mates.

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Species Overview

The royal dottyback (Pictichromis paccagnellae), also called the bicolor or false gramma dottyback, is a small marine fish reaching about 7 cm (3 inches). Its colour is striking and unmistakable: the front half electric purple, the back half bright yellow, meeting at a crisp, hard dividing line (the key feature distinguishing it from the gradual-blending royal gramma).

The royal dottyback is hardy, reef-safe, colourful, and inexpensive — and helps control reef pests like bristleworms — but it's bold and aggressive for its size, harassing shy, slow, or similar-looking fish, which is the defining husbandry consideration. It's rated beginner-friendly on care, with the challenge being its temperament and stocking. With good care it lives 5–7 years. For a reef with robust tank mates (and a keeper who stocks the dottyback thoughtfully), it's a tough, vivid, characterful jewel — and a useful pest-hunter. Note there are several dottyback species (orchid, neon, etc.) with varying temperaments; the royal dottyback is one of the feistier ones.

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Natural History and Origin

Pictichromis paccagnellae ranges across the Western Pacific, living on coral-rich reef slopes where it hides in caves and rubble and darts out to feed on zooplankton and small invertebrates. It's a secretive, territorial fish that claims a crevice and defends a patch of reef, hunting micro-prey and bristleworms from cover.

This cave-dwelling, territorial, hunting lifestyle is the basis of both its value and its temperament. Its appetite for bristleworms and small invertebrates makes it a useful biological pest controller, and its hardiness reflects an adaptable, opportunistic nature. But its territoriality and boldness — natural traits for defending a reef crevice — translate into aggression toward tank mates, especially shy, slow, or similar-coloured fish, in the confines of an aquarium. Many dottybacks are also protogynous hermaphrodites. Its colour, hardiness, pest-hunting, and feistiness all stem from this territorial, cave-dwelling reef life.

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Water Parameters

Royal dottybacks are hardy and adapt well to stable reef conditions. Mix salt with RO/DI water, target salinity with a refractometer, and add them to a fully cycled tank — confirm with the nitrogen cycle tracker and the water parameters reference. Their toughness makes them forgiving of minor fluctuations.

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Tank Setup Guide

Tank size

A royal dottyback is comfortable in a 30-gallon (115-litre) reef, with more space helping to dilute its aggression toward tank mates. While small, its feistiness means a too-small or sparse tank concentrates conflict.

Aquascape — caves and rock

Provide plenty of live rock with caves and crevices — the dottyback claims and defends a cave, hunts through the rock for pests, and shelters there. Abundant rockwork is essential both for its natural behaviour and for managing aggression (broken sightlines and territory let other fish stay clear). A mature reef with lots of structure suits it.

Filtration, flow, lid

Run a standard reef system. A lid is sensible (dottybacks can jump). A rock-rich reef gives the dottyback territory and gives tank mates refuge from its assertiveness.

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Feeding Guide

Royal dottybacks are carnivores that hunt small prey and readily take prepared foods.

What to feed

• Frozen mysis and enriched brine shrimp — readily accepted staples.
• Marine pellets/flake — most dottybacks take prepared foods eagerly.
• Reef pests — bristleworms and small invertebrates it hunts naturally.
• Copepods and small live foods — relished.

How often

Feed once or twice daily. They're eager, bold feeders (no risk of being outcompeted — quite the opposite). A varied diet keeps the vivid purple-and-yellow colour saturated. A healthy royal dottyback is bold, brightly coloured, and active around its cave.

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Behaviour, Aggression and the Gramma Look-Alike

The royal dottyback is bold, hardy, reef-safe, and a useful pest-hunter — but feisty and territorial for its size, which is the defining husbandry consideration. As it settles, it claims a cave and harasses shy, slow, or similar-looking fish, and it can bully tank mates well beyond its small size. This makes it "reef-safe" (no harm to corals/inverts) but potentially a problem for peaceful fish.

Management: add the dottyback last (so it doesn't establish dominance first), provide ample rockwork to break sightlines, choose robust tank mates that can hold their own, and avoid shy/slow fish (like firefish or mandarins) in smaller tanks. Critically, do not keep it with the royal gramma — they look similar (purple-and-yellow), see each other as rivals, and the more aggressive dottyback will harass the gramma; choose one or the other (the gramma's colours blend gradually, the dottyback's meet at a hard line). Good tank mates include percula clownfish, yellow tang, foxface rabbitfish, and robust reef fish. Keep only one dottyback per tank. Use the compatibility checker.

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Breeding Guide

Royal dottybacks (and dottybacks generally) are among the more achievable marine fish to breed — they're cave/crevice spawners where the male guards a clutch of eggs in a cave, and some species (like the orchid dottyback) are commercially captive-bred. Home breeding is possible for the dedicated keeper: a bonded pair spawns in a cave, the male tends the eggs, and the larvae (smaller and more demanding than Banggai cardinalfish fry) are reared on rotifers then baby brine shrimp.

It's more involved than mouthbrooding cardinalfish but more achievable than many marine fish, making dottybacks a reasonable intermediate marine breeding project. For most keepers, the royal dottyback is a hardy, colourful display fish; choosing captive-bred dottybacks (where available) supports the hobby.

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Health and Disease

Royal dottybacks are hardy, with the usual marine concerns reduced by quarantine and stability.

Marine ich (Cryptocaryon) and velvet (Amyloodinium) can affect them — treat in quarantine with appropriate therapy. Bacterial infections follow poor water or injury. Jumping is a risk — keep a lid. Otherwise they're robust; their boldness and bright colour are signs of good health.

Prevention: quarantine new fish, keep parameters stable, feed a varied diet, provide ample rockwork, use a lid, and stock thoughtfully around their aggression. Given those, the royal dottyback is a hardy, colourful, long-lived reef fish.

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Interesting Facts

• A jewel with attitude. Its crisp purple-and-yellow split makes it look like a far pricier fish, but it's cheap, tough, and feisty.
• Not the royal gramma. The dottyback's colours meet at a hard line and it's aggressive; the royal gramma's blend gradually and it's peaceful — never keep the two together.
• A pest-hunter. It controls bristleworms and small invertebrates, a useful reef service.
• Bold beyond its size. Feisty and territorial, it can harass much larger or peaceful fish — stock it last and with robust tank mates.
• Breedable. Dottybacks are among the more achievable marine fish to breed (some are commercially captive-bred).

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Bringing It Together

The royal dottyback is a vivid, hardy, inexpensive reef jewel that earns its place hunting bristleworms and adding bold colour — but its feisty, territorial temperament defines how you stock it. Give it a 30-gallon-plus reef with plenty of caves and rockwork, stable conditions, and a varied diet, and manage its aggression by adding it last, choosing robust tank mates, avoiding shy/slow fish, and keeping only one per tank. Above all, never keep it with the look-alike royal gramma — they fight as rivals (remember: dottyback = hard colour line and aggressive; gramma = gradual blend and peaceful). It pairs well with sturdy reef fish like the yellow tang, foxface rabbitfish, and percula clownfish, and is even a reasonable marine breeding project. Plan the build with the AI Tank Blueprint generator and the compatibility checker.