The aim of this study is to evaluate locally available algae Fucus vesiculosus, Ulva Intestinalis and Cerathophyllum demersum using biomethane potential laboratory tests. Mechanical pre-treatment (cutting) and washing are applied to study the effects on cumulative biogas yield. Fucus vesiculosus (cut and washed) produced 81.8 l CH4/kg VS, Ulva intestinalis (cut and washed) produced 92.1 l CH4/kg VS and Cerathophyllum demersum (untreated) produced 405.3 l CH4/kg VS. For marine algae, the effect of pre-treatments varies from 17 % to 44 %, for freshwater algae it varies between –12 % and 5 %. Best t-test and p values are for washed Ulva intestinalis. Results show that from three tested algae species, Cerathophyllum demersum is the most suitable algae for biogas production in Latvia, but more detailed analysis of environmental, economical and legal aspects is needed.