Fish Tank Gravel Complete Guide: Types, Colour, Depth

Gravel choice shapes more than looks — grain size drives fish behaviour, colour reflects or absorbs tank light, and depth determines whether waste mineralises cleanly or turns anaerobic. This fish tank gravel complete guide from Gensou Aquascaping at 5 Everton Park covers the common gravel types sold in Singapore shops, honest notes on colour choices that suit local livestock, and depth recommendations for planted and non-planted tanks. Most beginners buy the brightest gravel on the shelf and regret it within six months; better knowledge up front saves a rescape.

Natural Versus Coated Gravel

Natural gravel is tumbled river stone or quarried aggregate — unpainted, inert, usually grey, brown or tan. Coated gravel is dyed or epoxy-sealed with colours from blue to neon pink. Good coatings last years; cheap ones flake within months and release colour into the water. Stick with uncoated natural gravel for planted scapes and serious aquascaping; leave novelty colours for kids’ tanks.

Grain Size Matters

2-3 mm fine gravel suits corydoras and loaches that sift substrate for food. 3-5 mm standard is the all-purpose community tank size. 5-10 mm chunky gravel looks bold but traps uneaten food deep in crevices and starves bottom-dwellers. 10 mm plus is decorative only, not suited to fish tanks. Singapore shops label gravel by visual estimate rather than mm; bring a ruler or match against a known reference.

Colour Choices for Singapore Tanks

Dark gravels — black, dark brown, charcoal — make fish colours pop. Cherry shrimp on black substrate look twice as red as on pale gravel. Chili rasboras, neon tetras and discus all display better over dark. Light tan and cream gravels wash out fish colour but brighten dim corner-of-living-room tanks. Pure white gravel looks striking at first, algae-greens within a month and needs constant cleaning.

Gravel Depth for Non-Planted Tanks

Aim for 2-3 cm depth on non-planted community tanks. Enough to anchor decor and look natural, shallow enough to siphon clean in one pass. Deeper substrate in non-planted tanks develops anaerobic pockets that release hydrogen sulphide when disturbed — a lightly sulphurous smell during vacuuming is a warning to reduce depth. Flat or gently sloped front-to-back looks cleaner than artificial hills.

Gravel Depth for Planted Tanks

Planted tanks want 4-6 cm in the foreground rising to 6-10 cm at the back. Root-feeding plants like swordplants, cryptocoryne and vallisneria need depth for root runs. Use root tabs buried at 4 cm depth every 8 weeks for mineral supply. Combine gravel with a fertile layer below — fine gravel cap over ADA Amazonia or JBL Manado base creates the fertility of aquasoil with the appearance of gravel.

Washing New Gravel

Every bag of gravel, regardless of brand or price, needs rinsing before use. Dust and fine particles cloud the water for days otherwise. Rinse in batches in a bucket, agitating vigorously, pouring off cloudy water until it runs clear. 10 kg of gravel takes 30-40 minutes of rinsing. Tropical quarry gravel from Singapore hardware shops often needs longer rinsing than branded aquarium gravel.

Biological Load of Gravel

Gravel provides surface area for beneficial nitrifying bacteria — more than new hobbyists realise. A 60 cm tank with 4 cm of gravel carries as much bacterial colony as a medium canister filter. Never wash established gravel with tap water during maintenance — chlorine kills the biofilm and triggers ammonia spikes. Gravel vacuum inside the tank only; keep the biology intact.

Popular Aquascaping Gravels

Black Moon Sand (SGD 18/5 kg at Green Chapter) — fine black volcanic-looking gravel, excellent for iwagumi. JBL Manado (SGD 28/3 L) — porous clay pellets, planted-tank friendly. ADA La Plata sand (SGD 25/2 kg) — fine cream for wabi-kusa and riparium scapes. Seachem Flourite Black (SGD 45/7 kg) — fertile iron-rich clay gravel for planted tanks. Generic tan gravel (SGD 4/kg) at any hardware or aquatic shop.

Compatibility with Livestock

Corydoras catfish need soft fine gravel or sand — sharp chunky gravel wears their barbels down. Loaches and freshwater rays demand sand only; gravel damages undersides. Cichlids dig and rearrange anything smaller than 5 mm. Shrimp colonise any substrate but forage better in fine gravel with gaps for biofilm. Match gravel grain to your planned livestock, not the other way round.

Common Gravel Mistakes

Too deep in non-planted tanks leading to anaerobic dead zones. Too shallow in planted tanks starving root feeders. Coated colour gravel in serious aquascapes looking toy-like. Mixing grain sizes creating unnatural layering. Not washing sufficiently and spending a week waiting for cloudy water to clear. Using hardware-store granite aggregate that leaches silicates and raises GH.

Singapore Sourcing Summary

Generic gravel (SGD 4-6/kg): any aquatic shop, Serangoon North, C328 Clementi, Thomson shops. Black Moon Sand (SGD 18/5 kg) and ADA La Plata (SGD 25/2 kg): Green Chapter Jurong West. JBL Manado (SGD 28/3 L): Qian Hu. Flourite (SGD 45/7 kg): Polyart. Avoid hardware-store construction aggregate unless you know it is inert washed quartz.

Related Reading

• How to Clean Fish Tank Gravel Guide
• Freshwater Aquarium Sand Guide
• Aquarium Substrate Layering Guide
• Planted Tank Substrate Care Guide
• Gravel Vacuum Fish Tank Guide