Small round craters, dimples, or "fish eyes" in a cured epoxy floor are a surface-tension problem — the coating pulled away from a spot it could not wet out. The cause is contamination or outgassing, and both are preventable.
What Fish Eyes and Craters Are
Fish eyes are circular voids where wet epoxy retracted from the surface, leaving a crater. They form when the coating hits something it cannot bond to — typically oil, silicone, wax, or dust on the slab — or when air escaping the concrete (outgassing) punches through the film before it gels.
On a garage slab, the usual offenders are old motor-oil residue and silicone from prior sealers or lubricants.
Why Prep and Timing Prevent Them
Thorough diamond grinding removes surface contaminants and the silicones that cause fish eyes, while opening the concrete so trapped air can escape evenly. Installing during stable or falling temperatures (not a heating slab in afternoon sun) stops the outgassing that creates pinholes. Both are standard in a professional install — and missing from most DIY jobs, as our DIY vs. professional guide explains.
How an Affected Floor Is Repaired
A floor with widespread fish eyes or craters needs the affected coat abraded and recoated over a properly decontaminated surface. If craters reach the concrete or coincide with bubbling, we grind back further and rebuild — see our related bubbling and blistering fix.
Get It Right the First Time
Clean, ground, contaminant-free concrete and correct install timing eliminate fish eyes. Choose an installer who grinds rather than etches — our contractor guide shows what to ask.
Related Guides & Service Areas
Frequently Asked Questions
What causes fish eyes in an epoxy floor?
Surface contamination — oil, silicone, wax, or dust — that the coating cannot wet out, or air outgassing from the concrete. Both make the wet epoxy retract into craters.
Can fish eyes be sanded out and recoated?
Yes, if shallow. We abrade the coat, decontaminate the surface, and recoat. Deeper craters or bubbling require grinding back and rebuilding.
How do professionals prevent craters?
Diamond grinding removes contaminants and silicones and lets air escape evenly, and we install during stable temperatures to avoid outgassing.
Do you repair cratered DIY epoxy floors in Katy?
Yes. We decontaminate, re-prep, and recoat for a smooth finish. Call (281) 503-5313.