Substrate

Substrate selection profoundly affects fish behavior and health. Fine sand is essential for benthic species like corydoras catfish that sift substrate for food and may injure barbels on coarse gravel. Aragonite sand and crushed coral in marine aquariums acts as a pH buffer through dissolution. Nutrient-rich aquatic soils (ADA Amazonia, Tropica Soil) drive aquatic plant growth and establish the nitrogen cycle through initial ammonia release — an intentional process requiring a fishless cycling period. Substrate depth (minimum 6 cm for planted tanks) affects root development, oxygen diffusion, and the ratio of aerobic to anaerobic bacterial zones.