<p>We present an optical method for water remediation that uses laser-induced photothermal convection to capture large quantities of micropollutants suspended in water. Multimode optical fibers coated with photodeposited silver nanoparticles act as compact absorbers at 450&#xa0;nm. They convert light into localized heat, generating buoyancy-driven flows resulting in convective currents that transport microplastics and/or metallic microparticles towards the fiber tip. We evaluate three configurations: i) a flat nanoparticle-coated tip, ii) a coaxial dual-fiber array and iii) a tapered fiber to modulate the heating footprint and flow topology. We quantify the dynamics of capture versus optical power and nanoparticle loading using polystyrene latex and polymethylmethacrylate microplastics, zinc microparticles, and mixed suspensions. Optimal operation at 67 mW yields the aggregation of hundreds of particles within minutes, whereas powers &gt; 70 mW trigger boiling and release. Particle-tracking reveals approach velocities that increase with absorber loading, and finite-element simulations corroborate steep temperature gradients and convective streamlines consistent with the observed recruitment. Under high-load conditions, the same flows promote ordered colloidal domains, enabling pre-concentration. Compared with electrode-based or pressure-driven methods, this approach is simple, low-cost, and scalable, requiring only laser light and a photodeposited fiber. The results establish design rules (power, loading, and geometry) for deployable, material-agnostic optothermal collectors aimed at point-of-need water purification and environmental monitoring.</p>