Getting Green Hair Algae Under Control in Your Reef Tank

In this guide

Green hair algae, usually shortened to GHA by hobbyists, is one of the most common nuisance algae in the marine hobby, and also one of the most manageable once you understand what is feeding it.

What it looks like and why it shows up

GHA grows as fine green strands that can carpet rock and substrate within weeks. It thrives on the same nutrients that make your tank look green and healthy in the wrong way, mainly nitrate and phosphate, along with strong or prolonged lighting. Overfeeding, infrequent water changes, and an undersized or poorly maintained protein skimmer are the usual culprits.

Getting to the root cause

• Test nitrate and phosphate rather than guessing, since both your tap or RO source water and your tank water should be checked.
• Cut back on feeding and remove uneaten food promptly rather than letting it break down in the tank.
• Service your protein skimmer regularly. A skimmer that is not pulling dark skimmate is not doing its job.
• Trim the photoperiod to eight to nine hours a day, and check that ageing bulbs or LEDs are not drifting in spectrum.
• Improve water flow to eliminate the low flow dead spots where algae tends to establish first.

Removing what is already there

Manual removal is the fastest visible win. Twist the algae off rock by hand or with a toothbrush during a water change and siphon it straight out, since leaving loose strands in the tank just returns the nutrients they have absorbed back into the water. A clean up crew of turbo snails and an algae grazing fish such as a tang can help keep new growth in check, though they are a maintenance tool, not a cure for a nutrient problem.

Using macroalgae as competition

Growing a fast growing macroalgae such as chaetomorpha in a refugium gives GHA real competition for the same nutrients, and pruning the macroalgae regularly exports nitrate and phosphate from the system for good rather than just recycling them.

When to consider chemical treatment

Products containing fluconazole can knock back stubborn GHA within ten to fourteen days, but they treat the symptom, not the cause, and the algae usually returns if nutrient export and flow are not fixed. In India these products are not commonly stocked by local aquarium shops and generally need to be ordered online from specialist marine suppliers, so most hobbyists find it more practical to solve the underlying nutrient problem first.

Article content © Ravi Teja. All rights reserved.