We studied whether mixing crushed shell into sediment can help Pacific littleneck clams cope with acidic seawater. In a 90-day experiment, young clams grew better with shell material present, even under acidic conditions. The shell pieces raised sediment water acidity levels in a helpful way, and clam growth looked much like clams in normal seawater. This suggests a simple, practical way to protect valuable shellfish and support healthier coastal ecosystems.