Hagen Fluval Stratum Substrate for Planted Aquariums - Hagen Fluval Plant Stratum is the ideal substrate for planted aquariums, featuring a light non-compacting porous structure. Its ideal properties as an aquarium substrate are highly beneficial to nitrifying bacteria which rapidly colonizes the vast porous surface, providing optimal water quality for fish. Plant roots easily penetrate and spread within Fluval Plant Stratum allowing plants to flourish and obtain a variety of key nutrients.