For 5 years now we have a swimming pond of about 100 m³ of category 4 (= rather less plants, cleaning by circulating pumps, various filters and gravel areas, the edge area is covered with large stones). The pond is in the sun all day and has no shaded areas. Right next to it we have adjacent fields, vineyards and forest. These are all conditions that are very difficult for a swimming pond to remain balanced and algae-free through the year. Starting from the 2nd year we had also in regular intervals from May to September extreme algae loads (thread algae, floating algae). This year in April - after a very constructive discussion with Mr. Baumgartner - I used Mikroveda Pond with zeolite for the first time. At the beginning with a shock treatment with the recommended amount for the pond size. Then we added some oxygenating plants and within 2 weeks the pond was crystal clear. Algae has disappeared from all the stones and the pond plants have also lost their constant algae pads. So far we saw the stones and the plants so clear only with the pond plant. Since then I distribute in monthly intervals with the watering can 2l Mikroveda Pond with a 1/2 kg Zeolith mixed in the edge area on the stones to keep the quality of the water in any case. And despite the very hot months of May/June this year, the water is crystal clear throughout. The plants sprout and countless pond snails have settled. We have not had such a pleasure with our pond for a long time!