Algae IDs

Chaetomorpha spp.

A popular contained refugium crop for nutrient export and pod habitat.

Refugium algae · Green macroalgae

Quick ID

Tangled, springy green spaghetti-like strands; no leaves or creeping runner.

Benefits / uses

Growth uses dissolved nutrients; harvesting physically exports the captured material.

Problems / risks

Dense or dirty masses shade themselves, trap debris and can die back.

Will anything eat it?

Not the most palatable fish food; keep the crop protected in a refugium.

Products / equipment

Brightwell ChaetoGro supplies trace nutrients when needed. It contains no nitrate/phosphate and is not an algicide.

Common lookalikes

Hair algae is usually softer and attached; mixed masses may contain nuisance algae.

Care / control

Provide suitable light and flow, thin regularly and remove decaying strands.

Ulva spp.

A fast-growing refugium crop and edible macroalga; contain it deliberately.

Refugium algae · Display algae · Fish food

Quick ID

Thin green sheets, ruffles or narrow leafy blades; form varies by species.

Benefits / uses

Harvestable nutrient export, pod habitat and fresh herbivore food.

Problems / risks

Loose fragments can spread; grazing can strip a display planting.

Will anything eat it?

Many tangs and rabbitfish readily eat it; individual appetite still varies.

Products / equipment

Clean cultured Ulva is widely sold; appropriate lighting and harvesting matter more than an additive.

Common lookalikes

Blade Caulerpa has thicker fronds linked by runners; film algae forms a coating.

Care / control

Grow in a protected refugium, harvest regularly and remove loose or decaying pieces.

Gracilaria spp.; including long ogo forms

Useful food and ornamental growth; species differ in texture and grazing appeal.

Refugium algae · Display algae · Fish food

Quick ID

Red, burgundy or brownish branching stems; many ogo forms are fine and bushy.

Benefits / uses

Nutrient export when harvested, pod shelter and edible seaweed for herbivores.

Problems / risks

Can collect debris; loose growth needs containment and adequate circulation.

Will anything eat it?

Many tangs and rabbitfish eat soft ogo. Tougher pom-pom forms can be less readily grazed.

Products / equipment

Clean cultured red ogo is commercially sold; no chemical control needed when deliberately grown.

Common lookalikes

Pom-pom Gracilaria hayi has tougher, broader branches; Halymenia has flatter, softer blades.

Care / control

Keep moving water through the crop, prune and remove declining growth.

Caulerpa racemosa complex

Useful in a controlled crop, but invasive when it escapes into rockwork.

Refugium algae · Pest if escaped · Green macroalgae

Quick ID

Green bead-like branchlets attached to stems and creeping runners.

Benefits / uses

Fast growth can provide harvestable nutrient export and habitat.

Problems / risks

Runners spread into rock; reproductive events or die-back can foul the water.

Will anything eat it?

Some herbivorous fish eat it; palatability varies and runners can remain.

Products / equipment

Manual removal for escaped growth. No selective reef-safe chemical recommended; check local availability restrictions.

Common lookalikes

Green bubble algae has vesicles fixed to rock without a Caulerpa runner.

Care / control

Keep contained, prune the whole runner and remove whitening or dying growth.

Caulerpa prolifera

An attractive managed macroalga; keep runners away from coral rock.

Refugium algae · Display algae · Green macroalgae

Quick ID

Broad oval or strap-like green fronds joined by creeping runners.

Benefits / uses

Harvestable nutrient export and planted marine habitat.

Problems / risks

Spreads by runners; reproductive events and declining growth need monitoring.

Will anything eat it?

Some tangs and rabbitfish may graze it; do not count on fish for containment.

Products / equipment

Sold as cultured macroalgae. Physical containment first; check restrictions and never release aquarium algae outdoors.

Common lookalikes

Ulva has thin sheets without runners; seagrasses are flowering plants rather than algae.

Care / control

Grow in a contained area, prune runners and remove unhealthy material promptly.

Halymenia spp.; trade names vary

A colourful ornamental macroalga; verify the species sold under the trade name.

Display algae · Refugium algae · Red macroalgae

Quick ID

Soft red blades or fronds, often with orange-looking tips under reef lighting.

Benefits / uses

Colour, shelter and some nutrient uptake; harvest for actual export.

Problems / risks

Can tear, decline or be eaten; slower ornamental growth is not a guaranteed nutrient solution.

Will anything eat it?

Some herbivorous fish eat it, so protect valuable specimens from grazers.

Products / equipment

Clean cultured Halymenia is sold commercially; growth support rather than algicide is appropriate.

Common lookalikes

Gracilaria usually has more stem-like branches; several Halymenia species share the same nickname.

Care / control

Provide suitable light and gentle circulation; secure without crushing and prune declining tissue.