The activity pattern is recorded by new techniques of real-time video tracking of the benthic activity. Electronic intelligent sensors allow the time analysis of benthic numeric objects with intensive automated recording sessions. We record the natural behaviour of several animals over 24h cycles. We also look into possible antagonistic behaviour, i.e. how animals feed when they have tubes close to each other and when feeding may occur in the same patches. Comparison is made between active motile surface deposit feeders and tubicolous surface deposit feeders. Activities of Amphiura filiformis, A.chiajei (motile burried Ophiuroids) and Melinna cristata (tubicolous Polychaete) are extracted by image analysis and quantified. Amphiura activity is restricted to its deposit feeding mode and no suspension feeding is present in the experiments. We also examine how addition of phytoplankton to the sediment will affect the feeding activity and if Amphiura and Melinna can locate patches of food. Dynamics of the response to food addition is studied.