A huge effort has been made to clean the water of Lake Constance, know as the Bodensee in German, after the increased use of fertilizer on farmland in the area and urbanization around the water caused phosphate levels to shoot up.
By the 1970s and 1980s, authorities were measuring up to 90 micrograms per litre of phosphates – chemicals which cause algae to grow more than normal - and this leads to bigger fish as it pumps up the whole food chain.
Last year water returned to 1950s levels - around six micrograms per litre. The clean water is seen as a huge success and has done wonders for tourism in the area, but has made life very difficult for fishermen on the lake.
"Sometimes I go for weeks with only two fish in the net," said Gert Meichle.
The catch last year on the upper Lake Constance - the larger of the two lakes - was down on the previous year by between 40 and 50 percent. "At the moment I can still just cover my costs," said Meichle, but he admitted that if his wife was not also working he would have to stop and find something else.
Three decades ago, whitefish found in the lake would weigh about 500 grams at three years old - now they take four years to reach about 300 grams according to the Association of Baden Professional Fishers.
Only seven professional fishers can be found on the German, Baden-Württemberg coast - the eighth recently hung up his nets, unable to earn enough to make it work. Others have to supplement the proceeds from fish with other work.
The fishermen are discussing three possible ways to try to increase their catch - by allowing each boat more than the regulation six nets, by allowing them to have nets with smaller mesh so they can catch smaller fish - and the reintroduction of phosphates to the water.
The last suggestion found little enthusiasm at Baden-Württemberg's state government. "An environment ministry is there to improve the quality of the water, not to worsen it," said Franz Untersteller, minister in question.
He said dumping fertilizer in the lake would not only contravene European Union guidelines, it would also have risks for the ecosystem.
"I'm not throwing anything in there in order to make the fish fatter," said Untersteller.