Stop pond leaks permanently with this professional-grade MS Polymer Pond Sealant — specifically formulated for aquatic environments and rated 4× stronger than standard aquarium silicone. Whether you're sealing a concrete pond, repairing a crack in a stone or render surface, or bonding pond equipment, this MS300 polymer adhesive sealant delivers an industrial-strength waterproof bond in just 24 hours — and it works even in wet conditions.
Unlike standard silicone sealants that degrade rapidly in submerged environments, this hybrid MS polymer formula is specifically engineered for permanent underwater use. It's certified fish safe — safe for koi, goldfish, and all pond life once fully cured — making it the professional choice for pond repairs in the UK.
Technical Specifications
| Specification |
Details |
| Product Type |
MS300 MS Polymer Adhesive Sealant |
| Size |
300ml cartridge |
| Weight |
495g |
| Colour |
Black |
| Cure Time |
Skins in ~1 hour, full cure in 24 hours |
| Application |
Wet or dry conditions — works underwater |
| Bond Strength |
4× stronger than aquarium silicone |
| Fish Safe |
Yes — when fully cured |
| Solvent Free |
Yes |
| Paintable |
Yes |
| Weatherproof |
Yes — all-weather performance |
| Guarantee |
2 years |
| Suitable Surfaces |
Concrete, glass, metal, stone, ceramic, GRP, UPVC, fibreglass |
Key Features
- ✅ 4× stronger than silicone — MS polymer chemistry outperforms standard aquarium sealants
- ✅ Works underwater — can be applied to wet surfaces and even underwater
- ✅ 24-hour full cure — fast turnaround for urgent pond repairs
- ✅ Fish Safe once cured — certified safe for koi, goldfish, and all pond life
- ✅ Solvent-free formula — no harsh chemicals that could harm aquatic life
- ✅ Flexible when cured — won't crack or shrink with temperature changes
- ✅ Paintable — paint over once cured for a seamless finish
- ✅ Marine grade — engineered for permanent immersion in water
- ✅ Free UK Delivery
Ideal Applications
-
Leaking concrete ponds — seal hairline cracks and larger fractures permanently
-
Stone and render ponds — bonds to natural stone, pointing mortar, and render
-
Fibreglass / GRP ponds — seals delamination and cracks in fibreglass pond shells
-
Pond edging and coping — waterproof bond for capstones, tiles, and edging
-
Aquarium repairs — stronger alternative to traditional aquarium silicone
-
Fountains and water features — seals around fittings, pipes, and edges
-
Pond equipment — bonds pond skimmers, bottom drains, and return fittings to liner
How to Use
-
Clean the surface: Remove all algae, loose material, and debris. The surface can be damp but should be free of standing water where possible.
-
Load cartridge: Insert into a standard mastic gun. Cut nozzle to desired bead size.
-
Apply sealant: Apply a continuous bead over the crack or joint. Tool smooth with a wet finger or spatula.
-
Allow to cure: Skins in approximately 1 hour. Full waterproof cure achieved in 24 hours.
-
Refill pond: Once fully cured (24 hours), it is safe to refill with fish present.
Why MS Polymer Beats Silicone for Pond Repairs
Standard silicone sealants — even "aquarium grade" products — can degrade over time when permanently submerged, losing adhesion and allowing water to bypass the seal. MS polymer chemistry forms a permanent cross-linked bond that doesn't degrade underwater, making it the professional choice for lasting pond repairs. With over 333 UK customer reviews and a 2-year guarantee, this is the pond sealant British pond owners trust.
🐟 Fish Safe | 💧 Works Underwater | ⏱️ 24hr Cure | 💪 4× Stronger than Silicone | 🚚 Free UK Delivery
