At 500 microns, this is the liner to reach for when the pond isn't a seasonal or trial installation — it's a permanent piece of farm infrastructure you're planning to rely on for years. The added material thickness translates directly into greater puncture and tear resistance, which matters both during installation (handling, positioning over ground that's rarely perfectly smooth) and over years of continuous water pressure and exposure once it's in service.
This is also our standard recommendation for fish farming and aquaculture specifically — a liner failure in a fish pond isn't just a water-loss problem, it can mean losing livestock, so the extra durability margin over 300 or 400 micron is worth the additional cost for that use case. For a large-scale or commercial water storage pond where the cost of liner failure and replacement is high, 500 micron is generally the more economical choice over the full lifespan of the installation, even though the upfront cost is higher.