How to Choose Fish Tank Size Guide: Stocking First

Most Singapore beginners buy the tank first and the fish second — then discover their chosen species needs twice the volume. This how to choose fish tank size guide from Gensou Aquascaping at 5 Everton Park flips the order. Pick the fish, calculate the minimum footprint, then buy glass to match. Twenty years of retail floor conversations point to one truth: oversized tanks fail less than undersized ones, and the SGD difference between a 60 L and a 90 L is usually under $80.

Start With the Fish, Not the Glass

Write down the species you actually want — not the ones the shop is promoting that weekend. A pair of angelfish needs 150 L minimum. A single betta thrives in 20 L. Six neon tetras want 60 L of horizontal swimming. Stocking drives everything downstream: filtration size, heater wattage, lighting footprint and ultimately your weekly maintenance burden. A 200 L tank with ten tetras is easier to maintain than a 40 L crammed with the same school.

Calculate Adult Size Honestly

Shop tanks show juveniles. A 3 cm juvenile goldfish grows to 20 cm. A 5 cm silver shark reaches 30 cm within three years. Look up adult length, then multiply by six for minimum tank length. Bottom-dweller footprints matter more than water volume — a 100 L cube is worse for corydoras than a 60 L long. Footprint first, litres second.

HDB and Condo Reality Checks

Full tanks weigh roughly 1.3 kg per litre including substrate and hardscape. A 300 L setup loads 400 kg on a 1 m x 0.5 m footprint — within HDB floor load limits (generally 150-200 kg/m squared distributed) but concentrated enough to warrant a proper cabinet that spreads weight. Condo balconies are often limited to 100 kg/m squared distributed — tanks over 120 L belong indoors. Check your lease; some condos restrict tanks over 200 L entirely.

Lift, Stairs and Door Clearance

A 4-foot tank ships in a box roughly 130 cm long. Standard HDB lifts accommodate this diagonally; older blocks with pre-1985 lifts sometimes do not. Measure your lift internal diagonal before ordering. Walk-up units and landed stairwells complicate deliveries further — most retailers charge $40-80 for stair carries and refuse tanks over 5 feet without two men. C328 Clementi and the Serangoon North shops will size-check with a photo of your lift.

The Stocking Maths That Actually Works

Ignore the old “inch per gallon” rule — it breaks at both extremes. Use adult biomass and swimming space instead. For community fish under 8 cm, roughly 2 L per cm of adult fish length in a well-filtered, planted tank. Aggressive or messy species (cichlids, goldfish) need 3-4 L per cm. Always round up. A dozen 5 cm tetras therefore need 120 L on paper — a 90 L is workable with strong filtration, but 120 L gives stability margin.

Standard SG Sizes and Typical Pricing

Popular ready-made sizes in SG: 45 cm (30 L, $60-90), 60 cm (60 L, $90-140), 90 cm (150 L, $180-280), 120 cm (240 L, $350-500), 150 cm (450 L, $650-1000). Rimless low-iron glass from Anchor, OPTI or ADA-style runs 40-80 per cent more. Cube tanks (30/35/45 cm) suit shrimp and nano aquascapes. Bow-front and corner tanks look dramatic but restrict aquascaping options — rectangular remains the workhorse choice.

Filtration and Heating Follow Volume

Rule of thumb: filter rated for 4-6x tank volume per hour for planted, 6-10x for messy stock. A 120 L tank wants a canister rated 600-1200 L/h — an Eheim 2213 or JBL e702 sits well here. Heater wattage at roughly 2 W per litre in SG is overkill most months — you rarely need to heat, but a 100 W unit set to 26°C hedges against cold snaps and air-conditioned rooms. Budget filter and heater at 20-30 per cent of tank cost.

Upgrade Path, Not Upgrade Cycle

New hobbyists often buy a 30 L, outgrow it in six months, buy a 60 L, outgrow again, then finally settle at 120 L. Each jump costs $100-300 plus wasted substrate, decor and often livestock losses during transfers. Buying the 120 L first — even if you stock it lightly for a year — is cheaper and kinder to fish. If space and budget genuinely prevent this, pick an entry size that matches a species you genuinely want to keep long-term (betta in 20 L, endlers in 45 L) rather than a compromise stock you will replace.

Water Source and Change Logistics

SG PUB water is soft (GH 2-4) and chloramine-treated. A 50 per cent weekly change on a 300 L tank is 150 L to prepare, dechlorinate and haul — manageable with a Python hose to the kitchen sink if your tank is within 8 m of a tap. HDB layouts with tanks in bedrooms require bucket changes or long hoses. Factor maintenance into your size decision: if you will not commit to 30-45 minutes weekly, stay under 120 L.

Matching Size to Experience

First tank ever: 45-60 L for a betta or endlers, or 90 L for a small tetra community. Returning hobbyist: 120-180 L. Confident aquascaper: 240 L and up. Nano shrimp specialist: 20-35 L cube. There is no prize for starting big if you have never cycled a tank — but there is also no shame in skipping the 30 L starter and going straight to 120 L if your budget and space allow. This how to choose fish tank size guide has served hundreds of Gensou clients who now keep stable, stocked tanks they actually enjoy.

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