Test results showing record levels of dangerous parasites in Sydney's water are 'not believable at face value'' and the real culprits are harmless algae, a consultant to the inquiry into the contamination crises said yesterday. As the warning to boil all water was extended indefinitely, Dr Jerry Ongerth said the levels of cryptosporidium and giardia found in most recent Health Department samples were 'as high as you would find in pure raw sewage, probably higher''. His own tests, on the other hand, had found 'lots of algae of different species, some of which look very much like giardia and some of which look very much like cryptosporidium''.