String Algae & Clarity in 2,500-Gal Pond: Filter Maintenance

Commercially built 2,500-gal pond, upflow filter/waterfall, cleaned twice yearly, prefilter in skimmer. String algae and clarity issues persist. Owner asks about biofilter construction.

Filter Cleaning Frequency

Twice yearly is insufficient for 2,500 gal with fish. Clean quarterly or when flow drops. Always rinse media in pond water—tap water kills bacteria.

String Algae Management

• Manual removal (rake/net).
• Barley straw in filter flow.
• Floating plants for shade.
• Phosphate remover if tests high.

DIY Biofilter Design

Container → pump at bottom → lava rock → filter floss → peat → lava rock. Water upflows through layers. See George's filter page for photos.

More frequent, gentle cleaning + nutrient control = clearer water.