20 Gallon Hexagon Fish Tank Setup: Stocking and Design

This 20 gallon hexagon fish tank setup guide is written for Singapore hobbyists eyeing a vertical column aquarium for a condo corner or landed entryway. At Gensou Aquascaping, 5 Everton Park, the 20 gal (75 L) hexagon is the most popular specialty format we advise on because it slots into spaces a rectangular tank cannot. Here is how to build one that actually performs.

Dimensions and What Fits

A standard 20 gal hexagon measures roughly 45 cm edge-to-edge across the widest axis, with a height of 50-55 cm. Footprint area is about 1,200 cm² — half the swimming floor of a 20 gal rectangular “long”. Plan on taller swimmers and vertical hardscape because horizontal swim paths are limited.

Weight and Placement

Filled, the unit weighs 90-100 kg. That is comfortable on a purpose-built hexagonal stand or a sturdy sideboard rated to 120 kg. HDB parquet floors handle this without concern, but set the stand on a polystyrene underlay sheet to distribute point loads from the rim. Keep the tank 40 cm from walls to preserve the 360-degree viewing you paid for.

Filtration Choice

A small canister is the cleanest solution — the SunSun HW-302 (SGD 75 on Shopee) or Eheim Classic 2211 (SGD 160 at C328 Clementi) at 400-500 L/h gives the 6-8x turnover a tall tank needs to prevent dead zones at the bottom. Route the intake and spray bar along one rear panel to preserve the front-three viewing faces.

Heater and Lighting

A 50 W Eheim Jager (SGD 58) set to 25-26°C covers aircon cooling. For light, a Chihiros WRGB II 45 (SGD 280) mounted on an arm stand gives enough PAR to reach the substrate 50 cm below. Avoid clip-on fixtures — they leave the lower third dim and favour only Anubias and moss.

Substrate and Hardscape

Use ADA Amazonia v2 (SGD 48/3 L — one bag suffices) sloped from 5 cm at the back to 2 cm front. A single tall Seiryu stone (SGD 6/kg at Nature Aquarium Gallery Thomson) or slim Manten driftwood spire works as a central column viewable from all sides. Avoid triangular layouts that favour one panel.

Planting the Vertical Column

Anchor epiphytes — Anubias nana petite (SGD 8), Bucephalandra “Kedagang” (SGD 18/portion), Microsorum pteropus “Trident” — onto the central hardscape. Ring the perimeter with Rotala rotundifolia and Ludwigia repens stems to fill height. A foreground of Eleocharis acicularis “Mini” (SGD 14/pot) softens the front without stealing focus.

Cycling Schedule

Dose Dr Tim’s Ammonium Chloride to 2 ppm, run Seachem Stability daily for 7 days, and test for ammonia, nitrite and nitrate daily. In Singapore’s warm 28°C ambient, the tank cycles in 3-4 weeks — faster than temperate climates. Our fishless cycling step by step walkthrough covers the daily readings.

Stocking Plan

Respect the limited footprint. A balanced stock: 10-12 cardinal tetras (Paracheirodon axelrodi) at SGD 1.80 each from Y618 Aquatic for a horizontal-midwater school, plus a centrepiece pair of honey gourami (Trichogaster chuna, SGD 14/pair). Skip bottom-dwellers — the 1,200 cm² floor is too cramped for corydoras. Five Amano shrimp handle algae duty.

Singapore Sourcing

Tank: C328 Clementi carries 20 gal hexagons seasonally at SGD 180-220; custom from N30 Tank runs SGD 400-550 with matching stand. Livestock: Y618 Aquatic Serangoon North for tetras and gouramis. Hardscape and plants: Nature Aquarium Gallery Thomson for Seiryu and tissue cultures. Seachem Prime and test kits: Shopee for best pricing.

Maintenance Routine

Weekly 20% water change with temperature-matched PUB tap treated with Seachem Prime (SGD 22/250 mL). A long magnetic scraper (Flipper Nano, SGD 38) beats reaching through the top opening. Trim stem plants fortnightly — they grow fast in warm water under WRGB lighting. Rinse filter floss monthly; deep-clean media every 8 weeks in tank water only.

Common Mistakes to Avoid

Overstocking is the top issue — the vertical volume tricks owners into thinking they have more footprint than they do. Placing the hexagon flush against a wall wastes the format. And skipping the canister in favour of a cheap sponge filter produces visible bottom-third detritus that six-sided viewing makes painfully obvious.

Related Reading

• Hexagon Fish Tank Complete Guide
• Hexagon Fish Tank Stand Guide
• Fishless Cycling Step by Step
• Cardinal Tetra Care Guide
• Vertical Aquascape Design