What to buy, how to set up, and what to stock in planted aquariums. Equipment lists, sizing rules, stocking ideas, and the most common mistakes.
Planted aquariums reward aquarists who care about light, CO2, and substrate as much as they care about fish. The hobby splits into low-tech (no CO2, slow growth, hardy plants) and high-tech (pressurized CO2, EI dosing, fast growth, demanding plants). Most planted-tank failures happen at the low-tech / high-tech midpoint, where keepers light hard but skip CO2 - that combination feeds algae faster than plants. Pick a lane and commit.
Core stack: tank with substrate appropriate to your tech tier (ADA Amazonia, Caribsea Eco-Complete, or pool filter sand for low-tech); LED lighting tuned to your light tier; CO2 system if high-tech (regulator, drop checker, diffuser, 5lb tank); HOB or canister filter; heater; thermometer; GH/KH/pH/nitrate test kits; fertilizer (Thrive Aquatic, all-in-one for low-tech; EI dry salts for high-tech).
Light: 30-50 PAR at substrate for low-tech, 60-100 PAR for high-tech. Photoperiod 6-8 hours; longer photoperiods grow algae before plants. Filter: oversized canister (e.g. Eheim Classic 350 on a 40 gallon) or HOB rated 6x volume.
A planted community at 30-75 gallons typically hosts 20-30 small schooling fish (rasboras, tetras, ember tetras, chili rasboras), a few bottom-dwellers (corydoras or otocinclus), and a shrimp colony. Avoid plant-eaters (silver dollars, large barbs) unless the plant list is plant-eater-tolerant.
Most-common mistake: lighting hard without CO2 in a "low-tech" tank. The result is algae growing faster than plants. Either commit to CO2 (high-tech) or dial light back to 30-50 PAR and pick hardy plants (anubias, java fern, cryptocoryne).
Low-tech: $200-500 all in for a 20-40 gallon. High-tech: $600-1,800 for the same size with CO2, premium light, and EI dosing.
Low-tech planted tanks are excellent for beginners. High-tech (CO2-injected) planted tanks have a steeper learning curve.
A drop-checker for CO2. Without it you are guessing on CO2 saturation and most "mystery algae" problems are CO2 problems in disguise.
4-6 weeks for freshwater systems with bottled bacteria + an ammonia source. Plants help by absorbing ammonia directly.
Most freshwater tank types convert easily between each other - swap substrate, hardscape, and stocking. Brackish to fresh requires careful salinity reduction over 4-6 weeks.