DIY Aquarium Magnetic Frag Rack Build Guide: Reef Coral Mounting
Reefers in Singapore quickly outgrow the four or five frag plugs that came with the tank, and a commercial magnetic frag rack runs SGD 100-180 for what is essentially a slab of plastic with magnets embedded. A diy magnetic frag rack built from eggcrate, N52 neodymium magnets and a few screws costs about SGD 35 and holds 30-plus plugs without budging in flow. This diy magnetic frag rack walkthrough from Gensou Aquascaping at 5 Everton Park covers magnet sizing, food-safe encapsulation, and how to position the rack so corals get the right par without shading frags below.
Materials and Pricing in Singapore
You need a 30 by 20cm sheet of plastic eggcrate (around SGD 8 cut from a hardware shop in Sungei Road), four N52 neodymium magnets in 20mm by 5mm discs (Shopee SGD 12-15 for a four-pack), a small tube of food-grade aquarium silicone, a pack of nylon zip ties, and a sheet of 3mm acrylic offcut for the magnet sandwich. A handheld drill with a 6mm bit handles the frag plug holes. Total cost lands at SGD 30-38.
Why Build Your Own Reef Frag Rack
Commercial racks lock you into one hole spacing, usually too tight for medium frags. Building your own lets you mix tight rows for zoa frags with wider centres for SPS, all on one panel. The magnetic mount also lets you slide the rack up or down the glass to dial in light intensity as your corals colour up — particularly useful with hungry Acropora that need 250-400 par.
Step One: Cut the Eggcrate Frame
Trim the eggcrate to your target footprint with a fine-tooth saw or cable cutters. A 25 by 15cm panel suits most 90-litre reef tanks. Smooth every cut edge with sandpaper so you do not snag corallines or your fingers. Mark the four magnet positions in the corners.
Step Two: Seal the Magnets in Acrylic
N52 magnets rust spectacularly in saltwater, turning your white plastic orange within a week if water touches them. Cut two 25mm acrylic squares per magnet, sandwich the disc between them with a generous bead of marine silicone, and clamp until cure. The acrylic shell must be fully sealed on all six sides — pinhole leaks ruin the magnet inside a month.
Step Three: Mount Magnets to the Eggcrate
Attach the sealed magnet packs to the eggcrate corners with stainless steel screws or strong nylon zip ties. Test orientation before locking in — the matching outside magnet must pull through your tank glass without flipping the rack. Use a second sealed N52 of identical strength on the dry side as the holding magnet, and dress it in a soft cloth slip to protect the glass from scratches.
Step Four: Drill Frag Plug Holes
Standard reef frag plugs have 6-7mm stems. Mark a grid with 25-30mm centres for zoa and softie frags, 40-50mm centres for SPS and LPS. Drill cleanly through the eggcrate squares; if a hole lands on a junction, shift it. Aim for 25-35 holes on a 25 by 15cm panel.
Step Five: Install in the Display
Slide the rack against the back glass at mid-depth, where flow is moderate but light still reaches. Apex Acropora frags go up top, montipora at mid-level, zoanthids and mushrooms below the lighting hot spots. Reposition every few weeks until each frag colours up. Pair the rack with reef-grade lighting and current from aquarium pumps tuned to 30-50x turnover.
Step Six: Cure and Soak Before Use
Silicone needs a full 7-day cure before saltwater immersion. Skip this and uncured acetic acid leaches into your reef and stresses corals. After cure, soak the rack in fresh saltwater for 24 hours and inspect every magnet pack for swelling or moisture. Any cloudy interior means a re-seal is needed.
Maintenance and Long-Term Care
Coralline algae will encrust the rack within six months — let it. The pink crust actually adds visual cohesion. Pull the rack every quarter, soak in 10 per cent vinegar to dissolve any heavy buildup blocking frag holes, rinse in RODI and reinstall. Inspect the magnet packs annually for cracks. Replacement N52 magnets and silicone are stocked alongside frag tools in the maintenance tools section, and frag glue is in the water treatments range at Gensou.
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emilynakatani
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5 Everton Park #01-34B, Singapore 080005 · Open daily 11am – 8pm
