This is the most critical step. You must run your tank for 2–4 weeks with a source of ammonia to grow beneficial bacteria that neutralize toxic fish waste.
Often caused by too much light (keep it to 6–8 hours) or excess nutrients. The Complete Aquarium Guide - Fish, Plants and ...
Check a "compatibility chart" to ensure your fish won't nip fins or eat each other. 3. The Greenery: Aquatic Plants This is the most critical step
Use a liquid test kit to monitor Ammonia, Nitrite, and Nitrate. Ammonia and Nitrite should always be 0. tie them to rocks or driftwood.
Larger tanks (20+ gallons) are actually easier for beginners because the water chemistry is more stable.
Anubias and Java Fern. These are "rhizome" plants—do not bury them in substrate; instead, tie them to rocks or driftwood.