Majano anemones are small pest anemones that hitchhike into reef aquariums on live rock and coral frags. They’re brown to tan with green tentacles tipped in rounded, sometimes pink bulbs, and they spread aggressively enough to damage corals and take over rockwork. If you’ve spotted one in your tank, you likely have more coming, and removing them requires killing the entire animal down to its base tissue.
How to Identify a Majano Anemone
Majanos are small, typically under an inch across when fully open. Their body color ranges from brown to tan, and their tentacles are green with distinctive rounded, bulb-shaped tips that sometimes show pink or light coloration. This bulb tip is the easiest way to distinguish them from Aiptasia, the other common pest anemone in reef tanks. Aiptasia tentacles are longer, thinner, and taper to a point, giving them a more wispy, translucent appearance. Majanos look stockier and more compact by comparison.
They can also be confused with desirable anemones like small rock flower anemones or even tiny bubble-tip anemones. The key giveaway is their size, their tendency to appear in clusters, and their habit of popping up in spots you didn’t place them. If you see one on a frag plug or tucked into a crevice on live rock you recently added, it’s almost certainly a hitchhiker.
Why Majanos Are a Problem
Majanos sting. Like all anemones, they use specialized stinging cells in their tentacles to defend territory and capture food. In a reef tank, this means any coral growing near a majano gets repeatedly stung, leading to tissue recession, bleaching, or death in the affected area. Stony corals and soft corals are both vulnerable. Because majanos reproduce quickly and colonize rock surfaces, a few individuals can become dozens within weeks, crowding out the corals and invertebrates you’re actually trying to keep.
They’re also considered an aquatic invasive species in the wild. Hawaii’s Department of Land and Natural Resources lists the majano anemone as a marine invasive species, which gives you a sense of how effectively they spread once established.
Why They’re Hard to Remove
The single biggest challenge with majano removal is that any tissue left behind can regrow into a new anemone. Physically scraping or pulling them rarely works because they retract deep into holes and crevices in live rock when disturbed. Grabbing the visible portion leaves the base (called the pedal disc or “foot”) still attached, and that fragment regenerates. This means that careless removal attempts can actually make an infestation worse by splitting one anemone into two.
Whatever method you choose, complete destruction of the entire animal, including any tissue hidden inside the rock, is the goal.
Chemical and Injection Methods
The most common DIY approach is injecting a substance directly into the anemone’s mouth using a syringe with a fine needle (insulin syringes work well). Several liquids are effective:
- Kalkwasser paste: A thick calcium hydroxide paste applied directly over the anemone or injected into its oral disc. This is one of the most widely recommended options and is already used by many reefers for Aiptasia.
- Hydrogen peroxide: Injected into the mouth, it destroys the tissue on contact. Concentrated solutions (30%) are far more effective than the standard 3% drugstore variety, but they’re caustic enough to burn your skin, so handle with care. After the initial injection dissolves most of the visible tissue, hit any remaining flesh with a second dose to prevent regrowth.
- Lemon juice or apple cider vinegar: Both work on smaller majanos. The acid causes the anemone to essentially implode. Lemon juice is a practical choice for minor infestations with just a handful of visible anemones.
- Commercial products: Products like Aiptasia-X and similar commercial pest anemone treatments are formulated for this purpose. They deliver a thick paste that the anemone ingests, killing it from the inside. Results vary with majanos since they’re sometimes more resistant than Aiptasia to these products.
With any injection method, precision matters. You need to get the substance inside the anemone before it retracts. Working slowly, positioning the syringe near the mouth, and injecting in a single smooth motion gives the best results. If the anemone pulls back into the rock before you finish, wait for it to re-emerge and try again.
The Majano Wand
The Majano Wand is a purpose-built electronic device that kills pest anemones with a small electrical charge delivered through a probe tip. You touch the probe to the anemone underwater, and the current destroys the tissue. It’s effective for reaching anemones in awkward spots on rockwork where injection is difficult. The critical detail, as the manufacturer warns, is that you need to ensure the entire animal is killed. If any tissue survives, it regrows. This means you may need multiple applications on larger specimens or anemones that have wedged themselves deep into crevices.
Biological Control Options
Several tank inhabitants eat majano anemones, though none are a perfect solution. Matted filefish, butterflyfish, and peppermint shrimp all consume them. The problem is that once these animals discover standard aquarium food, they tend to lose interest in hunting anemones. This makes them most useful either at the very start of an infestation, when numbers are still low, or as a cleanup crew after you’ve knocked the population down through other methods.
Berghia nudibranchs are the most dedicated predator. These small sea slugs eat only anemones (both majano and Aiptasia) and nothing else. That single-mindedness is their strength and their limitation. They’ll methodically hunt down every anemone in the tank, but once the food supply is gone, they starve and die. They’re also expensive, which makes them a better final resort for persistent infestations rather than a first-line approach. If you go this route, adding several at once gives them the best chance of finding prey and reproducing before the population crashes.
Preventing Reinfestation
Majanos almost always enter a tank on live rock or coral frags. Dipping new corals in a pest treatment solution before adding them to your display tank catches many hitchhikers. Inspect frag plugs and the undersides of coral bases carefully. Even a tiny, barely visible anemone the size of a pinhead can establish a new colony. Quarantining new rock in a separate tank for a few weeks lets hidden anemones reveal themselves before they reach your display. Once you’ve dealt with a majano infestation, these precautions feel a lot less optional.