Well, what happened with my tanks is this:
I have 4 water tanks. One leaked so I separated it and it was like this for some years. New crew member found disconected water pipe and he happilly put it back were it was. After next fill of water the smell was this bad that you could not stay belowe the deck. After a while I found out what happened and we flashed the tanks about 10 times with baking soda and separeted the leaking tank again. Now, after all that the smell is still there and we can not stand it. My tanks are monel and I never had any problems with the smelly water. So, in short words the water in bad tank was just as bad as cespol tank and it got to the system!!!
Well, dont know what to do now and I will not give up sailing becouse of that. Any advice from anyone? Thanks