- Algae, BBA (black beard algae)
- A dark, bristly algae that grows on slow-flow areas and leaf edges — usually a sign of unstable or low CO2 rather than "too much light" on its own. See CO2 & lighting basics.
- Aquascape
- An aquarium arranged as a deliberate landscape — hardscape and plants composed as a scene, not just a habitat for fish.
- Biotope
- A tank built to accurately replicate one specific real-world location's water, substrate, hardscape, and species. See the Biotope style breakdown.
- Carpet plant
- A low-growing foreground species (dwarf hairgrass, Monte Carlo, glosso) planted densely to form a lawn-like ground cover.
- Dry start method (DSM)
- Growing carpet or emersed plants in a tank with no standing water for several weeks before flooding, so roots establish faster than they would fully submerged.
- Drop checker
- A small glass device that changes color (yellow to blue-green to blue) to indicate dissolved CO2 level — the standard way to gauge CO2 without a direct sensor.
- Dutch streets
- The straight or gently curved rows of a single plant species that make up a Dutch-style layout, each contrasting the next in color, texture, and height. See the Dutch style breakdown.
- EI dosing (Estimative Index)
- A fertilizer-dosing method that deliberately overdoses macro and micro nutrients on a weekly schedule, relying on a large weekly water change to reset levels rather than precise testing.
- Emersed
- Grown with leaves above the waterline rather than fully submerged — most aquatic plants grow faster and hardier this way, which is why the dry start method works.
- Flow
- The movement of water through a tank from filter output and any additional powerheads — even distribution prevents dead spots where CO2 and nutrients don't reach.
- Hardscape
- The non-living structural elements of a layout — stone and driftwood — placed before any planting begins. See hardscape placement.
- Iwagumi
- A minimalist style built from an odd number of stones (usually 3–5) and a single low-carpet plant. Japanese for "rock formation." See the Iwagumi style breakdown.
- Nano tank
- A small aquarium, generally under 10 gallons — often the entry point for aquascaping because it's cheap to experiment on and quick to rescape.
- Negative space
- Deliberately empty area in a layout — open substrate or water column left unplanted to give the eye somewhere to rest and the hardscape room to read.
- Oyaishi
- The "parent stone" in an Iwagumi layout — the largest stone, placed off-center, that every other stone's angle and size relates back to.
- Paludarium
- A tank that combines land and water in the same enclosure, usually connected by a slope or waterfall. See the Paludarium style breakdown.
- Photoperiod
- The number of hours per day the tank light runs — typically 6–8 hours for a planted tank.
- Rhizome
- A horizontal stem structure (found in anubias, java fern, bucephalandra) that must stay above the substrate — burying it causes rot.
- Rule of thirds
- A composition guideline placing the focal point at roughly one-third of the tank's width, rather than dead center.
- Stem plant
- A plant that grows as a vertical stem with leaves along its length (rotala, ludwigia) — typically planted in the background and trimmed regularly to control height.
- Wabi-kusa
- A ball of aquatic soil packed with plants and moss, grown emersed before being dropped into a tank — a shortcut to an already-established look on day one.
- Walstad method
- A low-tech, soil-based planted tank approach (named for Diana Walstad) that leans on plant mass and a natural nutrient cycle instead of CO2 injection or heavy dosing.