How to Build DIY Fish Tank Complete Guide: Glass and Silicone

Building your own tank is not cheaper than buying one — but it is how you get a bespoke size that fits an awkward HDB corner, or a low-iron rimless display no shop stocks off the shelf. This how to build DIY fish tank complete guide from Gensou Aquascaping at 5 Everton Park walks through glass specification, silicone selection and the bonding sequence that determines whether your tank holds water for 10 years or weeps at the base seam in six months. Patience matters more than skill.

Deciding Whether to Build

Before cutting glass, ask whether a standard tank from Sim Lim-adjacent glass shops or N30 Tank covers the need. DIY wins on custom dimensions, low-iron starphire glass panels, and one-off aquascape displays. DIY loses on convenience and cost for any standard size. A 60 by 30 by 36 cm tank costs roughly SGD 80-120 in materials to build and SGD 60-90 retail — so standard sizes are usually not worth the effort.

Glass Thickness and Panel Sizing

Glass thickness scales with tank height, not length. A 30 cm tall tank needs 5 mm glass; 36 cm needs 6 mm; 45 cm needs 8 mm; 60 cm needs 10 mm minimum with a brace bar. Use tempered glass only for the base if at all — silicone does not bond to tempered glass side edges. Low-iron (starphire) glass costs 50 percent more but shows plants and fish without the greenish tint of standard float.

Sourcing Glass in Singapore

Glass off-cuts from Sim Lim Square glaziers or the industrial glass shops along Kallang Road run SGD 8-15 per small panel. Cut edges must be seamed (smoothed) before bonding — a sharp edge cracks stress lines into the silicone. Request seamed edges when ordering. For low-iron glass, direct aquarium glass suppliers (Qian Hu trade channel or online Shopee imports) are more reliable than general glaziers.

Silicone Selection

Use 100 percent RTV silicone labelled “aquarium safe” — Dow Corning 999, Loctite SI 595 or Aquaseal. Qian Hu sells own-brand aquarium silicone in 310 ml cartridges at SGD 12-15, which suits small tanks under 60 litres. Avoid anything labelled “mould resistant” because the fungicide is toxic. Black silicone hides imperfect beads; clear silicone looks neater but shows every bubble. One cartridge covers roughly 1.5 metres of seam.

Cutting and Dry Fit

Lay the base panel flat on a level, clean surface — a sheet of MDF covered with a soft cloth works. Dry-fit all four side panels standing on top of the base, held with masking tape. Confirm right angles with a set square at each corner. Adjust until every joint closes without gaps wider than 1 mm. Any gap larger than 2 mm suggests inaccurate cuts and weakens the final seal.

The Silicone Bond

Wipe all edges with isopropyl alcohol (SGD 4 at Guardian) and let dry. Lay a 3 mm bead along each edge to be joined. Place panels into position one at a time, pressing firmly to squeeze silicone to a 1 mm uniform layer. Excess squeezes out — leave it; trim later. Support with masking tape and right-angle jigs cut from scrap aluminium angle iron (Home-Fix or Horme, SGD 6 per length). Work fast: silicone skins in 5-10 minutes.

Curing in Singapore Humidity

Silicone cures through atmospheric moisture, which Singapore provides in abundance. Full cure takes 48-72 hours; leave for a full week before any water contact for safety. Cure on a flat surface in a shaded area — direct afternoon sun on a bonded tank causes thermal expansion that disrupts the bond. The HDB laundry yard works if shaded; a bedroom corner with the fan on works better.

Interior Seam Bead

After the structural bond cures for 48 hours, apply a second silicone bead along every interior seam. This is the waterproofing layer. Lay a 5 mm bead, then smooth with a silicone shaping tool or a wooden ice-lolly stick dipped in soapy water. The bead should be concave, covering the full seam from glass to glass. This interior bead is what actually holds water; the structural bond simply holds glass in place.

Leak Testing

After one week cure, set the tank outdoors on a level surface, line with a towel beneath, and fill with tap water. Leave 24 hours. Any weep shows up as a dark damp line on the towel or a visible bead running down the glass. Small weeps can be redone — drain, dry fully for 48 hours, apply fresh silicone bead over the leak, cure again. Large leaks usually mean poor panel alignment and sometimes require rebuild.

Rim and Brace Bar Decision

Rimless tanks look cleaner but require thicker glass and meticulous levelling. A 60 cm rimless tank in 10 mm low-iron glass costs roughly SGD 180 in materials. Rimmed tanks with a plastic trim tolerate thinner glass and off-level stands more forgivingly. For first builds, a rimmed design with a cross-brace is safer; rimless is a second-build project once technique is confirmed.

Related Reading

• DIY Fish Tank Complete Guide
• DIY Fish Tank Stand Complete Guide
• Aquarium Silicone Guide Singapore
• Low Iron Glass Aquarium Guide
• Aquarium Glass Thickness Calculator