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    Sea cucumber

    Sea apple

    Pseudocolochirus spp.

    Avoid in most reef tanks

    Sea apple (Pseudocolochirus spp.)
    Photo: Marrabbio2, CC BY-SA 3.0, via Wikimedia Commons
    Group
    Sea cucumber
    Care level
    Advanced
    With corals
    Not reef safe

    What does the sea apple do in a reef tank?

    Filter feeder

    With corals: No

    How many should you keep?

    Not recommended

    One US gallon is 3.785 litres and one UK gallon is 4.546 litres, so a "per gallon" rule depends on whose gallon it means.

    What can go wrong?

    Releases toxins when stressed or dead that can kill fish and other life; eggs also toxic. Forum accounts of whole-tank wipe-outs; one view is that small tanks without carbon or skimming are most at risk

    Which tankmates are risky?

    Fish

    Fish that may eat or harass it.

    Take care (60)

    • Ocellaris clownfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Percula clownfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Clark's anemonefishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Tomato clownfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Maroon clownfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Neon gobyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Yellow clown gobyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Yellow watchman gobyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Orange spotted gobyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Hi-fin red banded gobyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Gold head sleeper gobyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Rainford's gobyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Lawnmower blennyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Bicolor blennyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Midas blennyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Tailspot blennyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Striped fang blennyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Royal dottybackA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Orchid dottybackA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Magenta dottybackA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Neon dottybackA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Banggai cardinalfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Pyjama cardinalfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Green chromisA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Yellowtail blue damselA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Blue damselA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Azure damselA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Humbug damselA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Yellow coris wrasseA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Six line wrasseA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Red head solon fairy wrasseA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Carpenter's flasher wrasseA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Melanurus wrasseA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Leopard wrasseA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Bluestreak cleaner wrasseA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • FirefishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Purple firefishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Scissortail dartfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Lyretail anthiasA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Bartlett's anthiasA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Royal grammaA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Yellow assessorA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Yellow tangA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Regal blue tangA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Kole tangA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Scopas tangA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Powder blue tangA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Coral beautyA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Flame angelfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Cherub angelfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Foxface rabbitfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Flame hawkfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Longnose hawkfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Falco hawkfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Yellowhead jawfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Mandarin dragonetA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Spotted mandarinA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Moorish idolA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Harlequin filefishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.
    • Copperband butterflyfishA stressed or dead sea apple can release toxins that harm fish; cover pump intakes.

    Other invertebrates

    Invertebrates it may harm, or that may harm it.

    None known.

    These checks follow the reasons fish and invertebrates clash: same species or genus, similar shape, mouth size, temperament, food, burrows, tank size and the order they are added. Individual animals differ; every source agrees on that.

    Sources

    1. Practical Fishkeeping (UK), essential cleaners for the reef tank (date not shown)Read 21 October 2026, read in full.
    2. Monster Fish Keepers and NJ Reefers sea apple threadsRead 21 October 2026, search summary only.

    Last checked . How we check

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    Tiger tail sea cucumber

    Holothuria hilla

    Care
    Intermediate
    Group
    Sea cucumber
    Corals
    Reef safe

    Photo François Michonneau, CC BY 3.0