| What It Is | Single-celled bubble macroalga |
| Looks Like | Shiny green spheres/bubbles on rock |
| Main Cause | Hitchhiker; nutrients help it spread |
| Difficulty | Easy to remove, easy to spread |
| Best Fixes | Careful manual removal + emerald crabs |
Overview
Bubble algae (Valonia or Ventricaria) shows up as glossy green orbs on your rock. The famous warning is real but often misunderstood: each “bubble” is essentially one giant cell, and if it ruptures it can release spores — so the goal is to remove bubbles without popping them into the tank. It’s not aggressive like Aiptasia, but left alone it multiplies and shades rock.
How to Identify It
Round to teardrop shiny green (sometimes silvery or dark) bubbles, from pinhead to marble sized, singly or in grape-like clusters, firmly attached to rock. The mirror-like sheen and perfect sphere shape are unmistakable — nothing else in the tank looks like a little green water balloon.
How to Get Rid of It
- Manual removal, intact — gently work each bubble off the rock whole, or lift the rock out and remove them over a bucket. Try to get the attachment point without bursting the sphere. If one pops, siphon the area.
- Emerald crabs (Mithraculus sculptus) — the classic bubble-algae grazer; many will pick and eat Valonia. Results vary by individual crab, so pair them with manual removal.
- Siphon while you pluck — remove bubbles with a siphon running nearby so any released spores get pulled out rather than settling.
- Keep nutrients moderate — won’t remove existing bubbles, but slows how fast new clusters form.
Prevention
Inspect and, where practical, remove bubble algae from new rock and frag plugs before they go in — it’s a hitchhiker. An emerald crab or two as standing clean-up crew keeps stragglers in check. Deal with a cluster while it’s small; a dozen bubbles is a five-minute job, a covered rock is not.
What Doesn’t Work
Popping bubbles in the tank “to pop them all”: the one thing everyone warns against — you may be seeding spores. Remove whole. Relying on the crab alone: emerald crabs are inconsistent; some ignore Valonia entirely. Ignoring it: slow-spreading isn’t no-spreading.
Helpful Livestock & Related Guides
Valonia macrophysa: The Clustered Bubble Algae
Valonia macrophysa is a bubble-algae species that grows in dense clusters of small-to-medium bright green bubbles, rather than the single large “sailor’s eyeball” bubble of Valonia ventricosa. It is the same nuisance alga at heart, and the same rules apply — with one twist: the clustered form ruptures more easily, so it takes an even gentler hand.
The golden rule still holds: do not pop the bubbles. Each bubble is essentially a single giant cell full of spores and cell contents, and bursting one releases them into the water to seed new outbreaks across your rock. Remove clusters intact instead:
- When possible, take the affected rock out and pluck the whole cluster off outside the tank; otherwise gently work intact clusters free underwater while siphoning to catch any that detach.
- Add emerald crabs (Mithraculus sculptus), which graze bubble algae — effective but hit-or-miss, and a bit less reliable on the tougher clustered Valonia.
- Starve it: Valonia thrives on excess nutrients, so lowering nitrate and phosphate slows its spread and helps the other methods win.
Because macrophysa spreads as many small bubbles, be patient and thorough — leftover cells regrow, so it usually takes a few rounds of careful removal plus nutrient control to fully clear.
Frequently Asked Questions
What is bubble algae?
Valonia: round, shiny green bubbles that grow on rock. Each bubble is essentially a single large cell filled with spores.
How do I remove bubble algae?
Remove whole bubbles without popping them, ideally by pulling the rock and taking them off outside the tank. An emerald crab will also graze it.
Why should I not pop bubble algae?
Popping a bubble in the tank can release spores that seed new growth elsewhere. Remove them intact whenever you can.
How is Valonia macrophysa different from regular bubble algae?
It is a bubble algae that grows in dense clusters of small-to-medium bubbles rather than one large bubble like Valonia ventricosa. Removal is the same — never pop it — but the clustered form ruptures more easily, so it takes an even more careful hand, plus emerald crabs and nutrient control.