Bicycle lamp-ray

A pressurised windowed chamber at the front of a bike containing luminous deep sea fish to enable the cyclist to find their way. The assemblage consists of a thick-walled chamber of metal with a window of something transparent but strong - i'm imagining something like artificial diamond, indium tin oxide, polycarbonate or just some special kind of glass, enclosing highly pressurised water in a reflective chamber. The water is saline and starts off oxygenated. Carbon dioxide and nitrogenous waste provided by the fish is separated by regularly decompressing some of the water and moving it into a separate non-pressurised chamber which is completely transparent and contains algæ and copepods. The algæ are fertilised by the nitrogen and convert the carbon dioxide back to oxygen and carbohydrates via photosynthesis. These are then repressurised and placed back into the fish chamber, which they then eat. The excess carbon dioxide comes out of the water and is converted via potassium oxide to potassium carbonate, which is gradually added to the water in small quantities, partly as a fertiliser for the algæ. The fish are a small species of hatchet fish. The idea is to provide an entirely closed ecosystem so as to avoid the danger of opening the chamber and consequent explosion. When not in use, a shutter is drawn down over the window and the algal compartment is left in sunlight to "recharge".