Describe the tank you actually have — its dimensions, light and carbon — and the plant index sorts itself into what will thrive, what will struggle, and what will melt. Most failed carpets aren’t a skill problem; they’re a high-light plant under a low-light lamp.
Internal dimensions in centimetres. Depth matters more than people expect — it decides how much light reaches the substrate.
The two things that decide what will actually grow. Everything else is fine-tuning.
Rough guide: a stock hood is usually low, a dedicated planted-tank LED is medium, and a high-output fixture on a timer is high.
Light falls off sharply through water. The same fixture that grows a carpet in a 30 cm tank often won’t in a 50 cm one, which is why identical shopping lists succeed in one tank and fail in another. The planner drops your effective light as depth increases and tells you what that leaves you with.