Rock Flower AnemoneThe rock flower anemone (Phymanthus crucifer, syn. Epicystis crucifer) is the anemone to start with — hardy, forgiving, and it stays put once it settles instead of wandering into a powerhead like host anemones do. It comes in a spectacular range of colour morphs and is kept purely for its own beauty, sold as colourful “gardens.” The one thing to be clear about before you buy: it's a Caribbean, NON-host anemone — clownfish do not host in it. Want a clown home? That's a bubble-tip. Want a bulletproof, gorgeous first anemone? This is it.
Care at a glance
| Adult size | Small — typically 2–4 in across, up to about 6 in. |
|---|---|
| Lifespan | Long-lived — sources cite many years to a decade-plus with good care (some claim far longer). As with all anemones, stable conditions decide it. |
| Minimum tank | ~20 gallons and up. Notably more forgiving than host anemones — it doesn't demand the very mature, months-old system a bubble-tip does, though a stable, established tank is still best. |
| Lighting | Moderate and forgiving — roughly PAR 50–150 is the sweet spot (it adapts across a wide range). Acclimate to brighter light gradually to avoid bleaching. |
| Water flow | Gentle-to-moderate, varied flow. Too much flow and it lets go and tumbles around the tank. |
| Placement | It tucks its foot into a rock crevice or the sand bed (often anchoring to buried rock, leaving just the disc showing) and, once happy, STAYS PUT — the big advantage over wandering host anemones. It can still relocate if conditions are wrong, so a roaming one means check your flow and water. |
| Temperature | 72–80°F (22–27°C); ~78°F is a common target. |
| pH | 8.1–8.4. |
| Specific gravity | 1.024–1.026 (~35 ppt). |
| Other targets | Standard stable reef parameters; zero copper, as with any invert. |
| Feeding | Photosynthetic PLUS small meaty foods — mysis, brine, finely chopped seafood — spot-fed about 1–2× a week for real colour and growth. It can survive on light alone, but feeding is better. |
| Temperament | Relatively mild — it has nematocysts and can sting a neighbouring coral or anemone and irritate sensitive skin, but it's far less aggressive than a host anemone. |
| Reef-safe | Generally reef-safe with a little spacing — it poses less threat than most anemones because it stays put. Leave a buffer, and note it will eat a small fish or shrimp that falls into it. |
| Natural range | Caribbean / Western Atlantic (much stock is now aquacultured, e.g. from the Dominican Republic). |
The fish store gets these wrong
Common myths, kindly corrected — no shame for having believed them.
- “My clownfish will live in it.” False, and the most common mistake — it's a non-host Caribbean anemone; clownfish (an Indo-Pacific group) don't host in it. For a clown home, keep a bubble-tip.
- “Blast it with light so it colours up.” No — intense light on a new one causes bleaching; acclimate gradually. It only needs moderate light.
- “More flow is better.” Too much flow makes it detach and tumble around the tank; it wants gentle-to-moderate, varied flow.
- “It's photosynthetic, so I don't have to feed it.” It'll survive on light, but small meaty foods 1–2× a week bring the real colour, growth and health.
Before you buy
- The right expectation: it does NOT host clownfish — it's kept for its own colour.
- A stable, established tank (~20 gal+) — more forgiving than a host anemone, but still wants stability.
- Moderate light (~PAR 50–150) and gentle-to-moderate flow.
- A rock crevice or sand spot for its foot to tuck into.
- An aquacultured specimen where possible — kinder to wild reefs.
Signs something's wrong
A struggling invert is usually telling you about water quality, acclimation, or (for shrimp and crabs) a fresh moult — here's what to watch for:
- Detaching and floating/tumbling — almost always too much flow or unstable water.
- Bleaching or fading colour — light stress (often too intense, too fast) or instability.
- A wide gaping mouth, “nubby”/retracted tentacles, or a deteriorating foot — signs of a sick specimen; avoid buying these.
- Failing to open or adapt after shipping — post-transport stress; watch it closely.
Never
- Never buy one expecting it to host a clownfish — it won't.
- Never blast a newly-added one with intense light — acclimate gradually to avoid bleaching.
- Never park it in high flow — it will detach and tumble.
- Never coral-dip an anemone during acclimation.
- Never dose copper with any anemone in the tank.
Common rock flower anemone questions
Will my clownfish host a rock flower anemone?
No. Rock flowers are Caribbean, non-host anemones, and clownfish (an Indo-Pacific group) do not host in them. They're kept for their own vivid colour. If you specifically want a clownfish host, look at a bubble-tip anemone instead.
Is a rock flower anemone a good first anemone?
Yes — it's widely considered the best beginner anemone: hardy, forgiving on light, flow and water, and it stays put once settled instead of wandering into a powerhead the way host anemones do.
Does my tank need to be as mature as it does for a bubble-tip?
It's notably more forgiving — it doesn't demand the very mature, rock-solid system a bubble-tip needs — but a stable, established tank (around 20 gallons or more) with steady salinity, alkalinity, calcium and magnesium is still strongly recommended.
Will a rock flower anemone crawl around my tank?
Usually not. Once it anchors its foot into rock or sand and is happy, it stays put. It only relocates if conditions are wrong — so if it starts wandering, check your flow and water stability.
Do I have to feed a rock flower anemone?
It photosynthesises and can survive on light, but it does far better with small meaty foods — mysis, brine or finely chopped seafood — spot-fed about 1–2 times a week for real colour, growth and health.
Is a rock flower anemone reef-safe?
Largely, with a little spacing — its sting is mild and it poses less threat than most anemones because it stays put. Give it a buffer from corals, wash your hands after handling it, and know it will eat a small fish or shrimp that falls into it.
Sources & further reading
This guide was written and fact-checked against these authorities. It's honest, general guidance — not a diagnosis, and not a substitute for an aquatic vet or your own test kit:
- Top Shelf Aquatics — How to Care for Rock Flower Anemones — size 2–4 in, decade+ lifespan, 20-gal min, PAR 80–150, gentle flow, stays-put placement, feeding 1–2×/wk, temp 75–80°F, pH 8.1–8.4, SG 1.024–1.026, NON-host, beginner difficulty, Caribbean origin
- Reef Builders — The Flower Anemone: A Hardy Caribbean Beauty — typical 3–4 in, Caribbean origin, hardy/beginner-friendly, foot-tucked-into-rock placement, wide light & flow tolerance, feeding ~1×/wk, mild sting, lower reef threat
- Saltwater Aquarium Blog — Rock Flower Anemone Care — PAR 50–150, moderate flow, weekly meaty feeding, nematocysts/sting, reef-safe with spacing, Caribbean origin, clownfish do NOT host, Easy difficulty, mistakes and warning signs
- Aquarium Specialty — Flower Anemones: Care, Feeding and Conservation — PAR 100–250, feeding 2–3×/wk, non-host (names true host species instead), Dominican Republic aquaculture sourcing
Written and fact-checked by The Coralkin Team against marine-aquarist sources — if your rock flower anemone is struggling, it's almost always water quality, acclimation or a moult — check those first and ask an experienced reefer. We never guess a care number.
🔬 Review status: team-written and fact-checked against cited sources · not yet reviewed by a marine vet. How we research & fact-check →