33 Gallon Long Tank Stocking Guide: Swimming Room Wins

This 33 gallon long tank stocking guide is written for Singapore hobbyists who bought the 48-inch footprint precisely for its horizontal swimming lane — and now want species that actually use it. At Gensou Aquascaping, 5 Everton Park, the question we hear most is “why not just get a 4-foot standard?” The answer: the shallow 33 cm height profoundly changes species compatibility in ways worth planning around.

Why Footprint Drives Stocking Choices

At 122x30x33 cm, the 33 long offers 4 feet of length in a tank only 33 cm tall. Angelfish and tall gouramis feel compressed. But shoalers that cruise horizontally — giant danios, SAE, hillstream loaches — get a genuine “river” experience impossible in a standard 30 or 40 breeder. Stock to this strength, not against it.

Centrepiece Species for the 48-inch Run

Siamese algae eaters (Crossocheilus siamensis) need swimming length — a group of 5 fits beautifully. Giant danios (Devario aequipinnatus) in a shoal of 8 turn the tank into a blur of motion. Rainbow shiners (Notropis chrosomus) work too but need slightly cooler 26°C, tricky in Singapore ambient.

Shoaling Mid-Water Options

Pair the headline species with 20-25 mid-water shoalers. Harlequin rasbora (Trigonostigma heteromorpha), espei rasbora (Trigonostigma espei), and ember tetra (Hyphessobrycon amandae) are Singapore-tap-friendly and hold shoaling behaviour in this footprint. Our best shoaling fish for Singapore tanks post covers the full list.

Bottom-Dwellers

The 122 cm of floor space suits a cory group of 10-12 (Corydoras pygmaeus or Corydoras habrosus). Hillstream loaches (Sewellia lineolata) add the station-holding algae-grazer niche — three to five individuals. Kuhli loaches (Pangio kuhlii) bring nocturnal charm; stock 6-8 to see natural behaviour.

Centrepiece Non-Shoalers

One or two standout fish add visual anchor. A pair of honey gourami (Trichogaster chuna) or a single German blue ram (Mikrogeophagus ramirezi) complement schooling traffic without territorial disputes. Skip angelfish — the 33 cm height is marginal for their adult fin span.

Shrimp and Snail Cleanup Crew

Amano shrimp (Caridina multidentata) in groups of 8-12 handle algae across the 48-inch footprint. Add 3-4 nerite snails (Neritina natalensis) for glass grazing. Avoid cherry shrimp if hillstream loaches are present — the loaches will outcompete them for biofilm.

Stocking Levels and Bioload

125 L of water supports a moderate bioload of roughly 30-35 cm of adult fish length. A worked example: 5 SAE (25 cm total), 8 giant danios (80 cm) — already at ceiling, so pick one or the other. Substitute 20 harlequins (100 cm including schooling density bonus) plus 10 pygmy cory and hillstream loaches for a gentler bioload.

Water Parameter Targets

PUB tap at pH 7.6-8.2 suits most of these species. For blackwater biotopes, dose Fluval Peat Granules in the canister (SGD 18) to drop pH to 6.5-7.0. Temperature 26-28°C is tolerable but push towards the lower end for hillstream loaches using a chiller or fan setup — our Singapore aquarium cooling guide details the options.

Avoid These Species

Any fish needing 40+ cm height (angelfish, discus, tall gouramis) is a poor 33 long match. Territorial bottom-dwellers larger than 10 cm (clown loaches, plecos over 12 cm) overwhelm the 30 cm front-to-back. Fast predators (arowana, tiger barbs in low numbers) hunt anything small. A well-executed 33 gallon long tank stocking guide always leans into the horizontal-lane strength rather than forcing tall species into a shallow tank.

Sample Complete Stocking Plan

For a planted Southeast Asian biotope: 22 harlequin rasbora, 10 pygmy cory, 5 hillstream loaches, 3 honey gourami, 10 Amano shrimp, 4 nerite snails. This loadout fills all four niches (surface, mid, bottom, glass) without overshooting bioload at week 12.

Singapore Sourcing Summary

C328 Clementi sells harlequin rasbora SGD 1.20 each, SAE SGD 4-6, pygmy cory SGD 4-6. Y618 Serangoon North stocks hillstream loaches SGD 12-18 and honey gourami SGD 8-12. Green Chapter Jurong West carries ember tetras SGD 1.50 and German blue rams SGD 18-25. Iwarna at Pasir Ris is strong on corydoras variety SGD 4-14. Nature Aquarium Gallery Thomson Road stocks premium F1 rams SGD 28-42. Polyart carries snails SGD 2-4 and nerites SGD 4. Carousell frequently lists shrimp colonies SGD 20-80 per bag. Shopee offers acclimation kits and Seachem Prime SGD 14-22.

Related Reading

• 33 Gallon Long Fish Tank Setup Guide
• Best Shoaling Fish Singapore Tanks
• Hillstream Loach Care Singapore
• Singapore Aquarium Cooling Guide
• Southeast Asian Biotope Ideas