QUICK STATS

Care Level: Easy to Moderate
Diet: Carnivore
Temperament: Semi-Aggressive to Aggressive
Reef-Safe: Yes, With Caution
Venomous/Toxic: No
Approximate Purchase Size: 1-2"
Approximate Max Size: Around 2.5-3"
Recommended Tank Size: 30 Gallons or Larger

PURPLE STRIPE DIADEMA

The Purple Stripe Diadema, also known as the Purple Stripe Dottyback, Diadema Dottyback, or Diadem Pseudochromis (Pseudochromis diadema / Pictichromis diadema), is a small but bold saltwater fish known for its bright yellow body and vivid purple stripe running along the top of the head and back. It is colorful, hardy, and extremely confident for a fish that could fit in a coffee mug.

Purple Stripe Diadema Dottybacks are popular because they stay small, adapt well to aquarium life, and bring strong color to reef tanks. They are usually visible once established and often claim caves, crevices, or sections of rockwork as their territory. Once they pick a spot, they may defend it like they have mortgage documents hidden in the live rock.

This species is generally considered reef-safe with caution. It should not bother corals, but it may harass smaller peaceful fish, similar-shaped fish, or delicate ornamental shrimp and tiny crustaceans. It is best added to aquariums with appropriate tank mates and plenty of rockwork. Tiny fish, massive attitude. Nature really does love a bad joke.

Note: Image is a representation of what to expect. The fish you receive may vary slightly in size, color, markings, stripe intensity, and overall appearance.

AQUARIUM REQUIREMENTS

AQUARIUM SIZE

A minimum tank size of 30 gallons or larger is recommended for a Purple Stripe Diadema. While some sources list slightly smaller minimums, a 30-gallon or larger aquarium gives this territorial fish more space and helps reduce aggression.

Because this species can become bold and defensive around its chosen area, extra rockwork and territory matter more than just water volume. In smaller tanks, dottybacks can become little purple-and-yellow tyrants with excellent hiding skills and no remorse.

HABITAT RECOMMENDATIONS

Purple Stripe Diadema Dottybacks do best in established aquariums with plenty of live rock, caves, crevices, and hiding places.

Aquascaping: Provide live rock with caves, ledges, overhangs, and narrow spaces. Dottybacks like to move in and out of rockwork and often claim a sheltered territory.

Substrate: Sand, fine aragonite, crushed coral, or bare-bottom systems can all work. This species does not depend heavily on the substrate.

Rockwork: Live rock is strongly recommended. It provides hiding places, territory, biological filtration, and natural hunting areas.

Tank Maturity: A mature aquarium is preferred. Stable water quality and established biological filtration help reduce stress and improve long-term success.

Tank Cover: A tight-fitting lid is recommended. Dottybacks can jump, because apparently even fish with caves still occasionally choose airborne stupidity.

WATER PARAMETERS

Purple Stripe Diadema Dottybacks are hardy once established, but they still need clean, stable marine conditions. “Hardy” does not mean “immune to bad husbandry,” despite what the hobby keeps trying to prove with tragic confidence.

Temperature: 72-78°F
pH Level: 8.1-8.4
Salinity: 1.020-1.026 specific gravity
Ammonia, Nitrite, and Nitrate: Ammonia and nitrite should remain undetectable. Nitrate should be kept as low as reasonably possible, ideally below 20 ppm.
Water Flow: Low to moderate flow is ideal. Provide enough water movement to keep the aquarium oxygenated and move waste toward filtration, while still allowing calmer areas inside rockwork for hiding and resting.

DIET

Purple Stripe Diadema Dottybacks are carnivores that should be offered a varied diet of small meaty marine foods. They are usually strong feeders once established and often adapt well to frozen and prepared foods.

PRIMARY DIET

Frozen Food: Offer mysis shrimp, enriched brine shrimp, krill, chopped clam, cyclops, marine blends, and other small meaty frozen foods. We at Summit City Coral prefer frozen foods such as LRS Reef Frenzy and PE Mysis.

Prepared Foods: High-quality marine pellets, carnivore pellets, and prepared meaty foods can help provide balanced nutrition. Smaller pellet sizes are best for juvenile or smaller individuals.

Live Foods: Copepods, amphipods, live brine shrimp, blackworms, and other small live foods can help encourage feeding, especially in newly introduced or shy individuals.

Small Meaty Foods: Finely chopped seafood and small crustacean-based foods can be offered in rotation. Avoid relying on only one food type, because variety is apparently the one reasonable demand fish nutrition makes before everything gets expensive.

FEEDING FREQUENCY

Feed small amounts 1-2 times per day. Make sure tank mates are also getting food, since dottybacks can be quick and pushy at feeding time. A fish this small should not have buffet security energy, and yet here we are.

COMPATIBILITY

Purple Stripe Diadema Dottybacks are best kept with tank mates that can handle a semi-aggressive fish. They may be peaceful in some aquariums, but they can also become territorial, especially in smaller tanks or around caves and rockwork.

COMMON TANK MATES

Fish: Clownfish, larger gobies, blennies, dwarf angelfish, wrasses, damsels, hawkfish, tangs in larger aquariums, and other semi-peaceful to semi-aggressive community fish.

Avoid: Very timid fish, tiny gobies, delicate firefish, small passive wrasses, newly introduced shy fish, and any fish likely to be bullied. Avoid housing with fish small enough to be viewed as prey.

Similar Species: Avoid keeping with other dottybacks, royal grammas, similar basslets, or similarly shaped territorial fish in smaller aquariums unless the tank is large enough and carefully planned.

Invertebrates: Use caution. Purple Stripe Diadema Dottybacks may eat or harass very small ornamental shrimp, tiny crabs, worms, and other small crustaceans. Larger cleaner shrimp may be ignored by some individuals, but this is not guaranteed.

Coral: Purple Stripe Diadema Dottybacks are considered reef-safe with coral and should not bother soft corals, LPS, SPS, zoanthids, mushrooms, clams, or anemones. The caution is mainly with small fish and small invertebrates, not coral.

BEHAVIORAL NOTES

Temperament: Semi-aggressive to aggressive. Personality varies by individual, but territorial behavior should be expected.

Territorial Behavior: Often claims caves, rock crevices, or a section of the aquascape and may defend it from other fish.

Reef Compatibility: Good for reef tanks with coral, but best listed as reef-safe with caution due to possible aggression and small invertebrate predation.

Visibility: Often becomes visible and bold once established. May dart in and out of rockwork throughout the day.

Hiding Behavior: Uses caves and crevices heavily, especially when newly introduced or startled.

Feeding Behavior: Usually a strong feeder and may aggressively grab food from the water column.

Aggression Management: Add more peaceful fish before adding a dottyback when possible. In smaller aquariums, this fish is often best added later in the stocking order.

Coloration: Typically has a bright yellow body with a purple to magenta stripe along the top of the head and back. Color intensity may vary depending on stress, diet, age, and lighting.

Small Fish Warning: Tiny gobies, firefish, and very passive fish may be harassed. This fish is small, but its attitude apparently comes in bulk packaging.

Jumping: A tight-fitting lid is recommended. Dottybacks can jump when startled or stressed, because apparently staying alive inside the aquarium was too straightforward.

ACCLIMATION PROCESS

This acclimation method helps reduce stress by gradually introducing the fish to your aquarium’s temperature and water chemistry.

1. TURN OFF THE LIGHTS & ATO

Turn off aquarium lights to reduce stress. If you have an Auto Top Off system, switch it off before starting acclimation.

2. FLOAT THE BAG

Float the sealed bag in the aquarium for 15-20 minutes to allow the temperature in the bag to equalize with the tank.

3. OPEN BAG, ADD FISH TO CONTAINER

Carefully open the bag and transfer the fish and shipping water into a clean bucket or container.

4. ACCLIMATE USING TANK WATER

Add 1/4 cup of tank water to the container every 5 minutes for 40 minutes.

5. TRANSFER FISH TO AQUARIUM

Once acclimation is complete, gently transfer the fish into the aquarium using a net or specimen container. Discard the shipping water. Do not pour shipping water into your aquarium.

6. REFILL THE AQUARIUM WITH SALTWATER

You may need to replace the saltwater removed during acclimation with fresh mixed saltwater.