Freshwater Planted Aquarium Basics

A planted aquarium is a living ecosystem where plants are the primary filtration. Healthy plants consume ammonia, nitrate, and phosphate directly, out-competing algae for nutrients. The result — when balanced — is crystal-clear water with minimal mechanical filtration.

The key variables to balance are light, CO₂, and nutrients. Too much light without enough CO₂ = algae explosion. Enough CO₂ with poor nutrients = slow growth. Getting all three right produces the lush Dutch or Nature Aquarium style tanks you see on social media.

Aquatic plant substrate is the foundation. Active substrates (ADA Amazonia, UP Aqua Soil, Fluval Stratum) contain nutrients and buffer pH down to 6.5–7.0, perfect for most tropical plants and soft-water fish. They also provide the soft, slightly acidic conditions that highlight fish colours.

Plain gravel or sand requires root tabs for rooted plants and full reliance on water-column dosing. It's a viable lower-cost option but less forgiving.

Layer: 6–8 cm of substrate depth allows root development for stem plants and crypts. Shallow substrate limits root growth and causes plants to melt.

Plants need PAR (photosynthetically active radiation) in the 20–80+ µmol/m²/s range depending on species. Low-light plants (anubias, java fern, crypts, mosses) thrive at 20–40 PAR. High-light carpeting plants (HC, hairgrass, glossostigma) need 60–100+ PAR.

A photoperiod of 7–8 hours is standard. Many planted tank keepers use a siesta schedule — 4 hours on, 3 hours off, 4 hours on — which has been shown to reduce algae without impacting plant growth.

For Singapore apartments without natural light, a quality LED (Chihiros, ONF, Twinstar, or the AI Blade) on a timer provides consistent results.

CO₂ is the limiting factor in most planted tanks. Plants absorb carbon from CO₂ during photosynthesis — without adequate CO₂, even well-lit, well-fertilised tanks grow slowly and algae wins.

Pressurised CO₂ (cylinder, regulator, diffuser) is the gold standard. Target 20–30 ppm dissolved CO₂, measured using a drop checker that turns lime green. Turn on CO₂ one hour before lights-on; turn off one hour before lights-off.

DIY CO₂ (yeast + sugar) is a low-cost alternative for small tanks but produces inconsistent levels. Excel (glutaraldehyde-based liquid carbon) is a CO₂ substitute that works for low-tech tanks but cannot replace pressurised CO₂ for high-demand plant species.

Plants need macronutrients (nitrogen, phosphorus, potassium) and micronutrients (iron, manganese, boron, and others). A complete fertiliser like Tropica Premium, Seachem Flourish Comprehensive, or the DIY EI (Estimative Index) method covers all bases.

In low-tech tanks (no CO₂), fertilise lightly and let fish waste supply much of the nitrogen and phosphate. In high-tech tanks with CO₂, dose aggressively — the Estimative Index approach deliberately overdoses and relies on weekly 50% water changes to reset.

The best fish for planted tanks are small, peaceful species that won't uproot plants or graze on leaves.

Best choices: tetras (cardinal, neon, ember, rummy nose), rasboras (harlequin, chilli), corydoras catfish (for substrate cleaning), otocinclus catfish (algae cleaners), small livebearers (endlers, celestial pearl danios).

Avoid: large cichlids (dig and uproot), goldfish (destroy plants at low pH), silver dollars (eat all leaves), most large pleco species (graze and damage stem plants).

Shrimp (neocaridina — cherry, blue velvet; caridina — crystal red/black) are excellent planted tank inhabitants. They graze on algae and detritus without harming plants, and breed readily in stable conditions.