One colony was collected in the inner harbour of Zeebrugge in December 1998 and could be held in an aquarium until June. A small colony was reared from medusa in May 2003. Planulae do not easily attach to plastic or glass recipients. Medusae are common in the inner harbour of Zeebrugge and the waterway to Bruges from half March until the end of May. They are between 1 and 4 mm high. Medusae are released from the hydroid in autumn, when water temperature is between 15° and 11°C. Medusae start asexual reproduction when water temperatures drop below 6°-7°C by developing up to 16 medusa buds. Each bud can also produce 16 new buds. Reproduction is explosive and reaches its maximum in April-May. Concentrations (due to the wind) of 70000 medusa per m³ were found along a quay-wall. Between 8° and 12°C there is sexual reproduction and at the end of May, when temperature is exceeding 15°C the medusa die and disappear from the plankton.
