Best Aquarium Glue: Superglue, Epoxy and Thread Compared

Table of Contents

• Why Choosing the Right Adhesive Matters
• Cyanoacrylate Superglue (Gel Formula)
• Epoxy Putty
• Cotton Thread
• Fishing Line
• Comparison Table
• What NOT to Use
• Tips for Each Method
• Frequently Asked Questions

Why Choosing the Right Adhesive Matters

Aquascaping constantly demands that things be attached to other things: moss to driftwood, Anubias to rock, stone to stone, wood to glass. The adhesive or fastening method you choose determines whether that attachment holds for years or falls apart within weeks — and, critically, whether it is safe for your fish and shrimps.

Not all adhesives are aquarium-safe. Many household glues, construction adhesives and general-purpose epoxies leach chemicals that are toxic to aquatic life. Using the wrong product can kill livestock and contaminate the tank for weeks.

At Gensou, we have tested and used every attachment method listed in this guide across hundreds of builds over 20 years. This guide covers the four main options — superglue, epoxy putty, cotton thread and fishing line — along with what to avoid entirely.

Cyanoacrylate Superglue (Gel Formula)

Cyanoacrylate (CA) superglue is the single most used adhesive in aquascaping. It is aquarium-safe, bonds almost instantly and works on virtually every surface you will encounter in a planted tank.

Key Properties

• Aquarium safe — Pure cyanoacrylate is inert once cured. It is the same compound used in medical skin adhesives.
• Gel formula essential — Always use the gel formula, not the liquid. Liquid superglue runs off surfaces and is impossible to control. Gel stays where you apply it.
• Turns white underwater — When cyanoacrylate contacts water, it cures instantly and turns opaque white. This is normal and can be concealed by plant growth. On dry surfaces, the bond remains clear.
• Instant bond — Sets in 5–15 seconds on dry surfaces. Underwater curing is even faster.
• Strength — Excellent for lightweight attachments (plants to hardscape). Adequate for stone-to-stone joints under moderate stress. Not suitable for heavy structural loads.

Best Uses

• Attaching mosses, Anubias, Bucephalandra and Java fern to driftwood and rock.
• Securing small stones in position within a rock arrangement.
• Gluing Dragon stone pieces into larger structures.
• Emergency repairs on cracked hardscape during maintenance.

How to Apply

1. Ensure both surfaces are dry. This is critical — superglue bonds poorly on wet surfaces and cures too quickly without a proper bond forming.
2. Apply a thin line or dab of gel to one surface.
3. Press the surfaces together firmly for 10–15 seconds.
4. Allow the bond to set for 30 seconds before handling.
5. Any excess that contacts water will turn white immediately — trim or hide with plants.

In Singapore, gel superglue is readily available at hardware shops (Mr DIY, Home-Fix), stationery shops and aquarium stores. Any brand works as long as the active ingredient is ethyl cyanoacrylate or methyl cyanoacrylate with no added fillers.

Epoxy Putty

For structural joints that need to hold heavy weight or resist force, epoxy putty is the professional choice. It is stronger than superglue, mouldable and available in aquarium-safe formulations.

Common Products

• Milliput — Two-part epoxy putty available in several colours (standard, terracotta, black). Mix equal portions, knead until uniform, apply and shape. Cures in three to four hours, fully hardens in 24 hours. Aquarium safe once cured.
• JB Waterweld — Specifically designed for underwater use. Can cure while submerged (unlike most epoxies). Sets in 15–25 minutes, full cure in one hour. Grey colour.
• Aquarium-branded epoxies — Various brands sell two-part epoxies marketed specifically for aquarium use. These are typically repackaged standard epoxies with a premium price tag.

Best Uses

• Building heavy stone structures (terracing walls, arches, overhangs).
• Attaching driftwood to rock bases so they do not float.
• Creating custom hardscape formations from multiple pieces.
• Securing equipment (pipe holders, diffuser mounts) inside the tank.

How to Apply

1. Cut equal portions of the two components.
2. Knead together thoroughly until the colour is completely uniform (two to three minutes).
3. Apply to the joint surfaces, pressing and moulding into shape.
4. For structural joints, create a generous fillet (wedge shape) around the contact point for maximum strength.
5. Allow to cure fully before submerging (check product instructions — typically 24 hours for standard epoxy, one hour for JB Waterweld).

Cotton Thread

Cotton thread is the original, low-tech method for attaching plants to hardscape. It is cheap, effective and has one significant advantage over glue: it biodegrades naturally once the plant has attached itself.

Key Properties

• Biodegradable — Natural cotton decomposes in water over four to eight weeks, by which time mosses and epiphytes will have rooted or gripped the hardscape on their own.
• Invisible over time — As the thread degrades and plant growth covers the attachment area, the thread disappears entirely.
• No chemical concerns — Pure cotton is completely inert in aquarium water.
• Requires wrapping — Less instant than superglue; you need to wrap and tie, which can be fiddly with small plants.

Best Uses

• Tying moss to driftwood or rock (wrap and tie every 1–2 cm along the attachment surface).
• Securing Java fern and Bolbitis rhizomes to hardscape.
• Situations where you want no permanent adhesive residue.

Fishing Line

Monofilament fishing line provides a permanent, nearly invisible attachment that does not degrade.

Key Properties

• Permanent — Does not degrade or weaken over time. The bond lasts as long as the line remains in place.
• Near-invisible — Clear monofilament (2–4 lb test) is virtually invisible once plant growth fills in around it.
• Strong — Will not snap under normal conditions. Suitable for securing heavier plants.
• Non-biodegradable — Does not break down, which is an advantage (permanence) and a disadvantage (must be cut to remove).

Best Uses

• Securing large moss portions to driftwood frames or rock faces.
• Attaching Riccia to stones or mesh panels.
• Tying plants in high-flow areas where thread might unravel before the plant attaches.

Comparison Table

What NOT to Use

Several commonly available adhesives are dangerous in aquarium environments. Never use the following:

• Hot glue (hot melt adhesive) — The bond weakens significantly in warm water (especially at Singapore’s 28–32°C). It may release plasticisers as it degrades. Pieces fall apart within weeks.
• Regular two-part epoxy (non-aquarium-safe) — Many standard epoxies contain bisphenol-A (BPA) or other chemicals that leach into water. Only use epoxies explicitly rated as food-safe or aquarium-safe.
• Construction adhesive (Liquid Nails, PL Premium) — Contains solvents and chemicals that are toxic to aquatic life. Never use these in any aquarium context.
• Silicone sealant (non-aquarium grade) — General-purpose silicone often contains fungicides or anti-mould additives (look for “mildew resistant” on the label — this means it contains biocides). Only use 100% pure silicone labelled as aquarium-safe.
• Rubber cement, contact cement, PVA glue — Not designed for submerged use and may release harmful compounds.

Tips for Each Method

Superglue Tips

• Buy multiple small tubes rather than one large one. Once opened, superglue tubes dry out within weeks, even when capped.
• Keep the nozzle clean by wiping with a dry cloth after each use and replacing the cap immediately.
• For attaching moss, apply tiny dabs (5 mm) every 2–3 cm rather than one large blob. This holds the moss flat against the surface and allows it to spread naturally.
• If the white curing bothers you aesthetically, apply the glue and press the plant down while both surfaces are still dry, then submerge. The bond forms clear on dry surfaces before it contacts water.

Epoxy Putty Tips

• Wet your fingers before handling mixed epoxy to prevent it sticking to your skin.
• For hidden joints, use standard grey Milliput. For visible areas, terracotta Milliput blends with Dragon stone, and black Milliput disappears against dark substrates.
• Sculpt the putty to match the surrounding hardscape texture before it cures — press rock or bark against it to imprint a natural surface pattern.

Thread and Fishing Line Tips

• When tying moss, wrap in a criss-cross pattern rather than parallel lines. The criss-cross holds more surface area of the moss in contact with the hardscape.
• Use dark-coloured cotton thread (brown or green) on dark hardscape. White thread on dark wood is conspicuous for the weeks before it degrades.
• For fishing line, use the lightest test weight that will hold — 2 lb monofilament is thin enough to be invisible and strong enough for any plant attachment.

Frequently Asked Questions

Is superglue really safe for aquariums with shrimps?

Yes. Pure cyanoacrylate (the active ingredient in gel superglue) is biologically inert once cured. It is used in medical applications to close surgical incisions and is approved for food contact. The key is ensuring it is fully cured before introducing livestock — wait at least five minutes after application (longer for large amounts) and rinse the area if possible. We have used superglue in hundreds of shrimp tanks at Gensou without a single adverse incident.

Can I use superglue underwater?

Technically yes — cyanoacrylate cures on contact with water. However, the bond formed underwater is weaker than a dry bond because the glue cures on the surface before it can penetrate the material. Additionally, the instant white curing creates a visible residue. For the strongest, cleanest bond, always apply to dry surfaces outside the tank, let the bond set, then submerge.

How do I remove superglue from aquarium glass?

Cured superglue on glass can be removed with a razor blade scraper (the same tool you use for algae). Hold the blade at a shallow angle and scrape gently. Acetone (nail polish remover) dissolves superglue but must never be used inside a tank with water or livestock. For removal from glass panels before setup, acetone on a cloth works quickly.

What is the best all-round adhesive for a beginner aquascaper?

Gel superglue. It is cheap (under $5 SGD), available everywhere in Singapore, instantly effective, aquarium-safe and covers 90% of attachment tasks you will encounter. Keep two or three tubes in your aquascaping toolkit and you will rarely need anything else. Add epoxy putty only if you are building heavy structural hardscape, and cotton thread if you prefer a no-glue approach for plant attachment.

Stock Up at Gensou

Having the right adhesive on hand saves time and prevents frustrating mid-build trips to the hardware shop. We stock gel superglue, aquarium-safe epoxy and thread at our Everton Park shop, alongside all the hardscape, plants and equipment you need for your next build.

If you would rather leave the gluing, tying and building to professionals, our custom aquarium service handles every aspect of the build, from hardscape assembly to final planting. Get in touch to discuss your project.

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