TankBud

Macroalgae

Macroalgae are the plants of a saltwater tank, grown in a refugium or the display to pull nitrate and phosphate out of the water. Chaeto is the workhorse, growing into a ball under a grow light, while caulerpa and others add form but can go sexual and crash if left too long. Each profile lists light, flow and how to harvest.

At a glance

Height
3.1–11.8 in
3.1 in (8 cm) to 11.8 in (30 cm); half the list stays at 5.9 in (15 cm) or under
Temperature
73–81°F
23–27°C, most of the list
Light
9 medium light
3 high light
Growth
2 slow growing
5 medium growth · 5 fast growing
Difficulty
7 easy
5 medium

12 plants

Start here

The macroalgae for a refugium

The chaetomorpha is marked beginner, a tangle of green filaments that floats and tumbles in a refugium, 7.9 inches (20 cm) across, and the usual first macroalgae. The caulerpa is marked easy and grows fast along runners at 5.9 inches (15 cm). The sea grapes are a caulerpa with round green beads. The red gracilaria is marked easy at 7.9 inches (20 cm), a red bush that tangs eat. The sea lettuce grows in green sheets under high light and soaks up nitrate. The Dragon's Breath is the showpiece, a red macroalgae marked medium at 11.8 inches (30 cm) for high light.

The rule

What macroalgae do

Macroalgae grow on the nitrate and phosphate a reef wants rid of, and the keeper harvests a handful every week or two, which is how a refugium exports nutrients. They run under a light on the opposite schedule to the display, which also holds the tank's pH steady overnight. Every macroalgae here lists CO2 as not needed. A caulerpa can go sexual and dissolve overnight, clouding the tank, so it is harvested before it gets old, and tangs, rabbitfish and angels eat most of them, so the display and the refugium are different places.

  1. 01

    Nutrient export

    Harvest a handful every week or two

  2. 02

    A reverse light cycle

    Lit at night, it steadies the pH

  3. 03

    No CO2

    Every macroalgae here lists none

  4. 04

    Fish eat it

    Tangs and rabbitfish clear a display macro in days

Display

Macroalgae for the display

The red grape algae is a red macroalgae with beaded branches, marked easy at 4.7 inches (12 cm). The Dead Man's Fingers is a spongy green Codium marked medium at 9.8 inches (25 cm). The watercress algae is a calcifying Halimeda, marked medium, that grows slowly in jointed green plates and needs calcium like a coral. The Maiden's Hair Algae grows in fine green tufts on rock at 3.1 inches (8 cm), marked medium for high light. The Money Plant is another calcifying green, marked medium at 5.9 inches (15 cm). The grape caulerpa is marked easy, the beaded caulerpa for the rock.

By the numbers

Smallest

  1. 01
    Maiden's Hair Algae (Chlorodesmis fastigiata)

    Maiden's Hair Algae

    Chlorodesmis fastigiata

    3.1 in (8 cm)
  2. 02
    Sea grapes (Caulerpa lentillifera)

    Sea grapes

    Caulerpa lentillifera

    3.9 in (10 cm)
  3. 03
    Grape Caulerpa (Caulerpa racemosa)

    Grape Caulerpa

    Caulerpa racemosa

    4.7 in (12 cm)
  4. 04
    Red Grape Algae (Botryocladia botryoides)

    Red Grape Algae

    Botryocladia botryoides

    4.7 in (12 cm)

Tallest

  1. 01
    Dragon's Breath (Halymenia durvillei)

    Dragon's Breath

    Halymenia durvillei

    11.8 in (30 cm)
  2. 02
    Dead Man's Fingers (Codium fragile)

    Dead Man's Fingers

    Codium fragile

    9.8 in (25 cm)
  3. 03
    Sea Lettuce (Ulva lactuca)

    Sea Lettuce

    Ulva lactuca

    9.8 in (25 cm)
  4. 04
    Chaetomorpha (Chaetomorpha linum)

    Chaetomorpha

    Chaetomorpha linum

    7.9 in (20 cm)

Easiest to grow

FAQ

Common questions

What is the best macroalgae for a refugium?

The chaetomorpha, marked beginner. It floats, tumbles, grows fast on nitrate and phosphate and cannot go sexual the way a caulerpa can.

How much light does macroalgae need?

Medium for most, high for the sea lettuce, Dragon's Breath and Maiden's Hair. A refugium light runs on the opposite schedule to the display.

Why did my caulerpa dissolve overnight?

It went sexual: an old, crowded caulerpa releases its contents and turns white and slimy. Harvest it every week or two so it never gets old, or keep chaetomorpha instead.

Can macroalgae live in the display tank?

The red grape algae, the Halimeda and the Dragon's Breath can, if nothing eats them. Tangs, rabbitfish and angelfish clear most macroalgae in days.

Do macroalgae need CO2 or fertilizer?

No CO2, ever. They feed on the nitrate and phosphate the fish produce, and iron helps the red ones; a tank too clean to feed them is a tank that no longer needs them.

How often do I harvest?

Remove a third to a half of the mass every week or two. Harvesting is the export; algae left to fill the refugium stops taking anything up.

Index

All macroalgae

Planning a tank?

TankBud checks stocking and water fit as you build a tank, then tracks water tests, reminders and photos once it is running.

Track your tanks

Maintain tanks for clients? See TankBud Pro