how are fish disease 7 parasites formed??

if you have a healty tank and 1 of the fish get stressed then catches a parasite how did the parasite get in the tank?

do we all have parasites in ours tanks then when a fish gets stressed they attack the fish witch leads to illness??

 

Depends on the parasite or disease.

Just like viruses and bacteria exist in the dry world so too do they exist in marine environments. A normally healthy fish has an immune system capable of fighting off infection. When they get stressed or exposed to a virulent strain their immune system can't keep up. Just like us when we get sick.

Most bacteria and viruses are water-borne, a few are contact based, and become a problem if a fish hits a rock and gets some scratches, usually the result of sudden fright where they run into something (not very common, fish are very careful to avoid hitting stuff, but it happens) or if they're itchy and rub against something. Many are also ingested when the fish eats.

As for parasites, MOST parasites require a host for at least one stage of their life cycle, and without a host will eventually die. Some parasites can host a healthy fish and like a disease the fish keeps it in check, but it's always there... others can live their entire life without a fish host. Most parasites, the ones that require a host, will die in weeks to months without a host, and they won't be able to reproduce, so the tank will clear out.... but any addition of rocks, coral, fish, inverts, etc can carry the larvae of a parasite, even one that's not techically "hosting" what it rides in on, it's still attached. That's why prophylactic dips and/or quarantine are important for everything, not just fish.

hope that helps. The subject of marine pathology is huge, but in general pathogens behave the same way in water as they do on land, so hygiene is important.

BUT! Do NOT put your clownfish in the dishwasher tho. They don't like it. ... so I have heard.

 

I highlighted my question. Could you elaborate I don't understand the process of a dip? Does this replace quarantine? Thanks