Fish lying on substrate has 2 categories: normal vs alarming. Normal substrate-resting: 1) Plecos + loaches + Otocinclus rest on substrate during day. 2) Bettas often rest on leaves or substrate at night. 3) Goldfish may rest at night. 4) Fancy goldfish (oranda, ranchu) sometimes rest from buoyancy issues. 5) Newly-acclimated fish may rest 1-2 days while adjusting. Alarming if NEW behavior: 1) Fast breathing + bottom-resting = water-quality issue. Test ammonia (target 0), nitrite (target 0), nitrate (target <30 FW, <10 reef). 2) Color fade + lethargy + bottom-rest = stress, disease, or end-stage condition. 3) Visible parasites (white spots, gold dust) + bottom-rest = ich/velvet. 4) Pinecone scales + bottom-rest = dropsy (often fatal). 5) Belly swollen + bottom-rest = constipation or internal infection. Diagnostic protocol: 1) Test water immediately. 2) Inspect for visible parasites or wounds. 3) Note rapid breathing rate (count gill movements per 10 sec - >40 is rapid). 4) Check for missing tankmates that may have died. 5) Use our symptom matcher to rank causes. 6) Quarantine + treat based on findings.
The full Q&A library, calculators, diseases, glossary, and interactive tools answer the most-searched aquarium questions.