How to Treat Periphytic Algae

Periphytic algae encrusts on the glass panes, décor, driftwood and rocks in an aquarium. Unlike unicellular algae, which floats in the water, periphytic algae, attaches to underwater surfaces. This nuisance algae thrive in the presence dissolved nutrients and strong light. Both marine and freshwater fish and sea-water invertebrates, such as corals, regularly release liquid metabolic waste into the aquarium and all aquariums require a light source, especially marine aquariums. The growth of periphytic algae is fueled under these conditions. You can rid your tank of this unwanted algae with a few basic husbandry regimes.

Things You'll Need

  • Aquarium
  • Gravel vacuum
  • Aquarium filter
  • Mechanical-filter material
  • High-quality activated carbon
  • Protein skimmer (marine aquarium only)
  • Marker pen
  • Reverse osmosis water (marine aquarium)
  • Fluorescent tube
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Instructions

    • 1

      Clean the bottom of the aquarium with a gravel vacuum. This is particularly important if the aquarium is overstocked because they typically are overfed because of the large number of fish. The combination of excess food and fish waste lying between the gravel particles become reservoirs for nutrients, which fuels the growth of periphytic algae.

    • 2

      Rinse or replace the mechanical-filter material in your internal or external filters. Clogged and dirty mechanical-filter material is a major source of both phosphates and nitrates in the aquarium water. Periphytic algae will thrive in the presence of both the nitrate and phosphate.

    • 3

      Change the activated carbon monthly and use only activated carbon that is low in phosphates. Activated carbon helps clean the water, but poor quality products are high in phosphates and will cause more harm than good.

    • 4

      Change at least 10 percent of the aquarium water each week, until you control the periphytic algae. Thereafter, change at least 10 percent of the water each month. Water changes dilute the concentration of unwanted nutrients, which allows algae to grow.

    • 5

      Place an internal protein skimmer in the tank, if it is a marine aquarium. Secure the skimmer to the inside-back glass pane of the aquarium with adhesive suction cups and turn it on. These filters export large amounts of nutrients from aquarium water and remove the algae's nutrient source, limiting growth.

    • 6

      Use a marker pen to make a small mark on the outside of the aquarium glass at the water surface. Top up water that has evaporated each day with reverse osmosis if you have a marine aquarium. Add reverse-osmosis water to the aquarium until it is at the level of the mark you made. Reverse-osmosis water is available from aquarium-supply dealers; it is pure water that does not contain phosphates and nitrates. Tap water is typically too high in dissolved organics, especially if you are already experiencing algae problems.

    • 7

      Replace old fluorescent lights. The light spectrum of the lights shifts with age and encourages unwanted algae.