The few freshwater species that exist in Portugal live in streams or flowing rivers, in other words, in conditions that are very different from those of a biological pool. Almost all of them are registered in the Red List, because they are rare and the destruction of their habitat and/or the pollution of streams and rivers strongly threatens the survival of these endemic species from Portugal or Iberian endemisms. On top of all this disgrace come the invasive exotic species introduced in Portugal in almost all of the territory that cause damage to aquatic flora and threaten the survival of the species here.
For those who like freshwater fish, the recently published book “Guia dos Peixes de Água Doce e Migradores de Portugal Continental” (Edições Afrontamento) is recommended. An interesting read for the summer, at the margin of a biological swimming pool, free from fish.
Because fish in the biological pool is not a good idea. First, many species of fish like to mess with mud and thus make the water cloudy, an unwanted effect. Second, other species feed on zooplankton, the small animals that are filtering the water in the biological pool. And, most importantly, there are no fish of the Portuguese fauna available in the market for purchase.