In this complete beginner guide for 2026, I walk you through the exact steps I’d take before you even buy your first fish tank. I start with the boring (but crucial) bit that loads of people overlook: where the tank is going to live. Keep it away from doorways (handles and corners don’t mix with glass) and away from big windows because the extra light and heat is basically an algae invitation. From there I get into tank size, and this is where beginners usually get it backwards. Small tanks aren’t easier—bigger water volume is more stable. My sweet spot for a first setup is around 20 gallons / 75L (roughly 60L and up is great). Then I break down the key equipment: filtration is the most important part of any aquarium, heater depends on the fish you choose, and lighting matters most if you’re growing plants. I also cover decor and substrate choices, water conditioners (dechlorinator + bottled bacteria), and why you should test your tap water before filling the tank properly. Finally, I go through buying your first fish (start small—around five fish), my simple “plop and drop” acclimation method, how to cycle using fish waste plus bottled bacteria while keeping ammonia/nitrite detoxed, and the long-term routine: weekly water changes and sensible filter maintenance (always rinse media in tank water, not under the tap).