• PRO Glue is a cyanoacrylate-based adhesive (i.e. super glue style) formulated for aquarium / reef / aquatic applications (i.e. “coral frag glue”) — meaning it’s designed to bond live rock, coral fragments (“frags”), aquatic plants, etc., often underwater.

• The “4 g” refers to the content (mass) of glue in each individual tube. Many product packs are composed of multiple 4 g tubes (so you can open only what you need, reducing waste)

• It is a "gel" form (thicker than a liquid cyanoacrylate), which helps in controlling application, preventing runs, and maintaining placement before curing.

PRO Glue has a long working time in air, lasting up to eight hours before it begins to harden, which makes it very practical for extended fragging or aquascaping sessions. Once it is placed underwater, it cures rapidly, bonding in about five to fifteen seconds. This quick reaction allows you to secure corals or plants directly in the aquarium with minimal waiting.

The glue comes in small 4-gram aluminum tubes, each one sealed with its own applicator nozzle and childproof ring. The positive-pressure tube design ensures that water does not backflow into the container when applying the glue underwater.

Its texture is an ultra-thick gel, much thicker than standard cyanoacrylate adhesives, which allows precise application without running or dripping. This also makes it possible to build up a bead of glue where needed to create stronger support for coral frags.

Although often marketed for marine aquariums and coral fragging, PRO Glue is equally suitable for freshwater tanks and for attaching aquatic plants, rocks, or small decorations. The formulation is described as high-strength and non-toxic, making it safe for use around sensitive aquatic life.

Finally, the use of multiple small tubes instead of a single large one is a deliberate choice—this prevents waste, since you can open only the amount you need while keeping the rest sealed and fresh for future use.

Typical Uses

• Coral fragging / mounting
  When you break or cut corals into fragments (“frags”) and want to attach them to rubble, rock, plugs, etc.

• Aquascaping / plant attachment
  Attaching plants (freshwater or saltwater) to rocks, wood, or other substrates.

• Small repairs / bonding in aquatic settings
  For bonding broken parts of underwater décor, ceramic, or small items in aquarium setups.

Steps when using PRO Glue 4g

1. Prepare surfaces
   Make sure both surfaces you are gluing are clean, dry (if possible) and as free of algae, detritus, or water films as feasible.

2. Apply small amount
   Because the glue is thick, a small amount suffices. You don’t want to flood the joint.

3. Press / hold
   Bring the surfaces together and hold in place for a short moment. In water, bonding begins in ~5–15 seconds, but full strength may need more time.

4. Allow curing
   Avoid disturbance in the area while the glue sets. Though the quick reaction helps, giving it a few minutes to firm up is wise.

5. Underwater working
   Due to the special tube design, you can even apply the glue while immersed (i.e. underwater) without the tube being compromised by backflow.

6. Use only required tubes
   Since tubes are small (4 g), open as many as you need to reduce wastage.

7. Storage / shelf life
   Keep tubes sealed and stored in a cool, dry place to maintain glue effectiveness. (As with most cyanoacrylates, high humidity, heat, or exposure to air may degrade performance over time.)

Advantages

• Extended working time out of water (8 h) gives flexibility during longer sessions (fragging, layout)

• Fast underwater curing means you can work in situ, with minimal delay.

• Thick gel consistency helps with precision, prevents runs or drops.

• Modular small tubes reduce waste, especially if you only need small amounts.

• Non-toxic claims make it safer for use in aquariums with live organisms (though always good to rinse or avoid excess).

Limitations

• Bond strength limits
  While strong, it may not be sufficient for large, heavy objects or in high-flow areas. For such cases, epoxy or mechanical bonding may be preferable.

• Penetration / Gap filling
  Cyanoacrylate gels are less effective for wide gaps or irregular shapes where deeper penetration is needed.

• Curing behaviour in different water chemistry
  Very high or low pH, certain additives, or high levels of organic compounds may interfere with bonding. (As with many adhesives, results may vary.)

• Shelf life / moisture sensitivity
  Cyanoacrylates generally are sensitive to moisture; if tubes are degraded or partially exposed, performance may decline.

• Not a substitute for structural adhesives
  For heavy-duty structural bonding outside aquarium hobby use, you should consider adhesives engineered for those loads.

Safety, Handling, and Compatibility

• As a cyanoacrylate derivative, caution is needed: avoid skin contact (instant bonding), avoid inhaling fumes in enclosed areas, use in a ventilated space.

• Many cyanoacrylates produce a mild exothermic reaction when curing; avoid applying in thick beads on sensitive materials.

• Be mindful of curing heat if applying on or near living tissue—fast curing adhesives may generate heat.

• Rinse any excess around live organisms if possible.

• Check compatibility with plastics or materials prone to crazing (some glues may cause stress cracks in certain plastics).