Aquarium Plants

Planted tanks are not a sub-hobby — they are a better way to keep fish. Live plants consume nitrate, compete with algae for light and nutrients, provide cover for shy species and spawning sites for egg-scatterers, and turn a glass box of water into something that actually looks alive. The myth that planted tanks are harder than unplanted ones is wrong: a properly planted low-tech tank is more stable, less work, and more forgiving than a bare glass box with a plastic ornament. The guides in this section cover how to do it without pressurised CO2, without expensive fertilisers, and without the obsessive testing that the high-tech aquascaping scene pretends is mandatory.

The most useful distinction in the plant hobby is low-tech versus high-tech. A high-tech tank runs pressurised CO2, high light, and daily fertiliser dosing; growth is explosive, algae is suppressed by plant competition, and the aquarist is essentially running a chemistry experiment. A low-tech tank runs ambient CO2, moderate light, and nutrients from fish waste and the substrate; growth is slower, the tank is more stable, and the aquarist does water changes instead of dosing. Both can be beautiful. Low-tech is what 90% of fishkeepers actually want, and it is what every guide in this section assumes unless it says otherwise. Start with Low-Tech Planted Tank for the framework.

Three things decide whether a plant lives or dies in your tank, and none of them is fertiliser. First, light: plants need a certain amount of usable light (measured in PAR, not in watts or lumens) to photosynthesise. A cheap LED that looks bright to your eyes may produce almost no usable PAR. The aquarium lighting guide covers what actually matters. Second, substrate: rooted plants need nutrient-rich substrate (soil, aquasoil, or root tabs); epiphyte plants (anubias, java fern, bucephalandra) need to be attached to wood or rock and will rot if buried. The Walstad guides cover soil substrates in depth. Third, plant choice: a plant that wants high light will slowly melt in a low-tech tank no matter how much fertiliser you add. The easy aquarium plants guide lists species that actually thrive at low PAR.

The Walstad method deserves a special mention. Developed by Diana Walstad, it uses a soil substrate capped with gravel, a small fish population, and modest light to create a tank where plants do most of the filtration. Done correctly, a Walstad tank can go months between water changes, requires no CO2 and no fertiliser, and grows plants that refuse to grow in standard gravel setups. The Walstad nano tank guide scales the method down to 5–10 gallon tanks; the planted 10-gallon Walstad is the worked example. The self-sustaining bowl guide takes the logic to its extreme — a heavily planted, low-bioload tank that genuinely runs without a filter.

Algae is the plant hobby’s bogeyman and the most common reason people quit. The honest answer is that algae is not a problem to be eliminated but a symptom to be read. Green spot algae means phosphate limitation. Hair algae means excess light or iron. Black beard algae means fluctuating CO2 or organic pollution. Cyanobacteria means poor flow and detritus. Every algae type tells you what is wrong with the tank; the algae guide walks through diagnosis and the fixes that work long-term, not just the chemical nukes that mask the problem.

Aquascaping is where planted tanks become an art form, and it intimidates new aquarists who have seen the IAPLC entries. It should not. The principles behind a good aquascape — the rule of thirds, depth through layering, contrast in leaf shape and colour, negative space — are learnable in an afternoon and applied over years. The nano aquascaping guide covers the fundamentals at the small tank sizes most people actually own, and the nano tank plant guide lists the species that work in tanks under 10 gallons.

A note on fish-plant interactions: many fish will eat or uproot your plants. Goldfish and silver dollars will mow through most species in days; large cichlids will dig up rooted plants; some barbs and tetras nibble fine-leaved species. The peace lily and betta guide covers one specific plant-fish pairing that works without soil or substrate; for general stocking, check the species guides before assuming your fish will leave your plants alone.

How to use this section

If you have never kept a planted tank, read in this order: Easy Aquarium Plants for species that will not die on you, then Low-Tech Planted Tank for the framework, then Walstad Method if you want a tank that mostly runs itself. If you are already planted and fighting algae, jump to the algae guide. If you are setting up a nano tank, read the nano plant guide before buying anything.

Pair the guides with the Walstad Soil Calculator (which calculates the soil volume needed for your tank dimensions) and the Walstad Bowl Planner (which sizes a self-sustaining bowl by plant mass and bioload). Both tools exist because guessing soil depth and stocking density is how new Walstad tanks fail — arithmetic prevents the most common mistakes.

Species-specific plant profiles are coming. Java fern, anubias, java moss, amazon sword, cryptocoryne, hornwort, duckweed, and the floating plants each deserve a page of their own — adult size, light needs, propagation, and the fish that will and will not eat them. The coming-soon cards below show what is in progress. Until then, the easy plants guide and the nano plant guide cover most of what you need to start.