Designers have found a way to make a building self-sustainable – and it involves covering said structure in what looks like green scum. The material that coats the BIQ apartment complex in Hamburg, Germany, is in fact cultivated algae.

Created as part of this year’s International Building Exhibition, the BIQ house – the name is a fusion of “bio” and “intelligence quotient” – has more than 100 glass tanks integrated into its south-east and south-west faces. These contain millions of microalgae suspended in a water solution, resulting in a green hue that could be enchantingly otherworldly or a little icky, depending on your point of view.

Like in lava lamps, bubbles regularly course through the tanks. It’s not just for effect as they carry carbon dioxide and nutrients to feed the algae. Ever so often, the plants are harvested and fermented to produce fuel. Energy is also generated via the glass panels, which absorb and convert light into heat.

Four out of 15 residential units have been rented and occupied since the apartment became fully operational in April. The inhabitants may be living with algae-covered windows – shade-providing, no less – but, so far, no one has complained about what seems to be life in a technologically advanced fishbowl.