The purpose of this thesis is to investigate the relationship between hobby associations (or clubs) and Internet-based forums, using the aquarium hobby as a case. The thesis has its starting point in the following research question: Today, aquarists may pursue their interest not only in clubs, but also on discussion forums online. Seen through the lens of communications theory, what then characterises the two forms of social intercourse and the relationship between them? What boundaries are set by the new possibilities of information technology and late modern society as regards the survival of hobby associations in the future? This abstract summarises the studies performed in this thesis and the consequent results. Club and forum members are essential and thus had to be pivotal. For this reason, a three-part empirical study with emphasis on the members was initiated. The study consisted of an observational visit at an aquarium auction, a gathering and analysis of numerous “threads” from two specific forums – Akvarieviden.dk (AV) and Akvariesiden.dk (AS) – and finally, a thoroughly worked out questionnaire on these two forums. First, however, some important analyses of modernity and modern life put forth by Anthony Giddens, Zygmunt Bauman, and Manuel Castells were examined carefully. Niklas Luhmann was incorporated as well for his understanding of communication along with Tim O’Reilly who provides a description of the modern Internet, web 2.0, and Mark Granovetter who has a very interesting sociological theory on network tie quality. The keywords of this examination were globalisation, fluidity, network-based individualism, threats, privatised faith in the future, life as individual project, abstract trust, and consumerism. As for web 2.0, the keywords were user-involvement, interaction, participation – innovation in assembly. The Internet has become fluid as well, the release cycle has ended, and permanent yet ever-changing beta-versions are now standard. Data have become central because web 2.0 is all about servicing the user. Accordingly, tools and techniques for utilising those data in the best possible way are crucial. Returning to the three-part study, the auction painted a picture of aquarists as somewhat nerdy types, but also revealed a broad social acceptance in this hobby. However, it was also discovered that there might be a tendency towards “closed circles” in some aquarium clubs. The most important finds in the analysis of the threads were that some forum members considered the umbrella organisation of the aquarium clubs to be out-dated and too bureaucratic; that young members tend not to do voluntary work in the clubs; that this hobby is not trendy among adolescents; that club meetings were old-fashioned; and that the Internet was seen generally as a competitor of the clubs because it makes for easy and cost free access to information. At the same time, though, members also eagerly discussed the benefits and cosiness of being a club member. The questionnaire tested a number of hypotheses and discovered lots of facts on the members of this hobby and their views on clubs and forums, the most important being the members’ diverging images of clubs (cosy, old-fashioned, few people) and forums (many people, easy, modern, lots of activity), and a surprising tendency to rank practical-personal needs above social needs when asked to associate meeting of needs with clubs and forums. This was contradictory to the threads where members emphasised the physical-social aspect of clubs as the most important one. The aquarists generally claimed to know very little about the activities of local clubs, and 74 % noted that a club had never contacted them. 123 out of 131 participants thought that forums and clubs could not be seen as competitors – this was also contradictory to the thread study. This thesis concludes that there seems to be a divide between what aquarists say and do: They praise clubs, but stick to forums anyway, roughly speaking. This could be explained by the clubs’ poor communication and old-fashioned ways along with a general tendency to romanticise an old idea of community. It is suggested that clubs have two options: to do nothing if change is unwanted or to seek renewal by creating a new “fluent” type of hybrid club based on some communicative and structural changes (e.g. organic work forms, less formalisation, integration of web 2.0) and the Internet as central platform. The closing of this thesis is an article (targeted at aquarists) that conveys its results.