Species Catalogue

Carnivorous aquatic plant used as a fine-leaved carpet alternative. Forms a delicate bright-green lawn. Requires CO2, high light, and soft water. Rewarding when established.

Dense, dark grey-to-black tufts that cling stubbornly to plants, hardscape, and equipment. One of the most frustrating nuisance algaes for planted tank keepers. Caused by CO₂ fluctuation and low or inconsistent carbon dioxide levels. Spot-treat with liquid carbon (Excel) or hydrogen peroxide.

Dense, rough-textured mats of dark green filaments that blanket pond plants and surfaces. Common in outdoor ponds and highly nutrient-rich tanks. More coarse and branched than soft hair algae. Difficult to eradicate fully — physically remove as much as possible before treating with algaecide or reducing nutrients aggressively.

A blue-green or red-brown slime that coats the substrate, plants, and glass with a slimy, foul-smelling mat. Technically a bacterium, not true algae. Caused by low nitrates, poor flow, and organic waste. Responds to a 3-day blackout combined with the antibiotic erythromycin or hydrogen peroxide treatment.

Red, purple, or dark blue-green slime mats that smother the sandbed and rockwork with a slimy, oxygen-depleting film. Technically a bacterium. Caused by low nitrates, poor flow, and high dissolved organics. A 3-day blackout, hydrogen peroxide spot-treatment, and improved flow usually break the cycle.

Feathery, fern-like dark green algae that is notoriously difficult to eliminate — one of the most persistent reef tank nuisances. Resistant to most herbivores. Best controlled by raising magnesium to 1500–1800 ppm for 2–4 weeks (magnesium treatment). Sea hares will consume it but are not a permanent solution.

Iridescent green spheres that appear harmless in small numbers but rapidly colonise rock if left unchecked. Emerald crabs are the most effective biological control. Do not pop bubbles — they release spores and worsen the outbreak. Manual removal requires extracting the entire holdfast; even fragments regrow.