DIY Biological Filter for Algae Control: Low-Cost, Low-Maintenance Solution

Build Your Own Biofilter

Use a plastic tote (recycle-bin size). Place the pump at the bottom. Cover with lava rock. Add a nylon bag of pond peat. Top with more lava rock. Finish with a layer of filter floss (air-conditioner filter material). Water flows up through the media, culturing beneficial bacteria that consume ammonia and nitrite.

Why It Works

The peat buffers pH and releases humic acids that inhibit algae. Lava rock provides massive surface area for bacteria. Floss polishes the water.

Maintenance

Rinse floss weekly in pond water. Replace peat annually. Never clean lava rock with tap water—chlorine kills bacteria.