Portugal is one of the countries in Europe where fish is very important, whether in the sea or on the plate. Freshwater fish are less appreciated, either in rivers or on plates. What about fish in ponds or small lakes? In principle there are no. There are species of freshwater fish introduced in Portugal, such as Sunfish, Catfish and Gambusias. Some are so bad for the aquatic environment that their classification as invasive species is more than justified and the possession of these species of fish is prohibited, with good reason.

The Iberian peninsula is very poor in native freshwater fish species living in ponds and this is the main reason why biological pools never harbor and should never have fish. Nor Gold Fish, because these belong to the carp family whose members always like to touch the substrates and consequently raise the mud deposited at the bottom of any pond. The result is constantly cloudy water and a release of nutrients that threatens the good quality of any pond. Therefor, biological pools are always ponds without fish!

With newts, frogs, frogs, tortoises, dragonfly larvae, water beetles and even water snakes, a biological pool becomes a habitat for so many living beings that are harmless and do not interfere in any way with the water quality. Thus, the water stays transparent and inviting and the virtual lack of fish is more than compensated for.