Thank you Johnarthur, I will try to see what I can find here - visit to a few local pet shops would help as well. You see I suppose that my biology knowledge is pretty good but as you know all topics are very specialised - aquatic hobby, microbiology etc so let me just say I am a quick learner

I was told that fish are often sick in spring ... again British weather

Will keep you posted. Jumping to his illness - I was giving him Octozin for 7 days everyday with 50% water change. He was very bloated didnt move then got better.Now I am afraid to keep him w/o drug - so Im just reducing dose - is it okay or shall I stop and see how he is?