Aquatic plants serve multiple roles: nitrate uptake (lowering bioload pressure), oxygenation, cover for shy species, breeding sites for spawning fish, and visual depth. The hobby splits into low-tech (no CO2, lower light, slow growth) and high-tech (pressurized CO2, high light, dosed micronutrients, aggressive growth and trimming) approaches.
Low-tech staples: Anubias (nana, barteri, congensis, pinto), Java fern (narrow leaf, needle leaf, trident, windelov), Cryptocoryne (wendtii, beckettii, parva, balansae), Vallisneria (jungle val, italian val, corkscrew), Sagittaria, Bucephalandra (multiple varieties), Amazon swords (bleheri, ozelot, red flame). All thrive at 30-50 PAR without CO2 supplementation.
High-tech demands: carpeting plants (Monte Carlo, HC Cuba, dwarf hairgrass, dwarf baby tears), red stems (Ludwigia repens, Rotala wallichii), demanding mosses (riccia, peacock moss). These need 100-150+ PAR with pressurized CO2 at 25-30 ppm during the photoperiod.
Plants need macronutrients (N, P, K) and micronutrients (Fe, Mn, Zn, Cu, B, Mo). Two dosing approaches: Estimative Index (EI) for high-tech setups (heavy weekly dose + 50% water change) or lean dosing for low-tech tanks (small daily/weekly doses). Pre-mixed liquids (Seachem Flourish, Tropica Premium, Easy Green) cover most needs.
Anubias barteri or Anubias nana. Both attach to wood/stone (no substrate needed), thrive at low light without CO2, are completely fish-proof (even cichlids leave them alone), and propagate by simple rhizome division.
Not for low-tech species (Anubias, Java fern, most crypts, Vallisneria, Amazon swords). Yes for high-tech species (carpeting plants, red stems, demanding mosses). Most tanks can be successful without CO2 if you stick to the right species list.
Tissue-culture and emergent-grown plants almost always melt (lose leaves) when transitioning to submerged growth. The rhizome/root mass survives and regenerates submerged-form leaves over 4-8 weeks. Trim melted leaves to encourage regrowth.