Help - Fish Emergency

OK so my tank has been established for 5 years, 20 gal, no problems. I had 1 loach and 2 mollies.

A few days ago, I got 3 cory cats. Within a day, they had all died.

Now today, my beloved loach has died as well, and the tank water smells absolutely awful - of rotten eggs. It is also cloudy, and this is really unusual for it. I am panicking a bit, and have done 2 water changes with gravel siphoning as well as Aquasafe and Prime.


Did the cories bring a disease into my tank? I really don't want my mollies to die, I don't know what to do. Please help

EDIT: Also there were clear eggs all around the rI'm of the tank.... I have smushed them all. No idea what they are

 

What kind of filtration are you using? If it is not ug and the bed is three inches or deeper I would say you had a buld up of anarobic bacteria and a release of hydrogen sulfide gass.

 

What kind of filtration are you using? If it is not ug and the bed is three inches or deeper I would say you had a buld up of anarobic bacteria and a release of hydrogen sulfide gass.

Sorry I don't know what ug means, its a filter for 40 gallons I think and mine is a 20 gal tank, and the bed is about an inch and a half deep.
I think you might be right about the hydrogen sulfide gas and bacteria, what should I do about it?

 

UG=Under gravel.

At an inch and a half I do not think hydrogen sulfide gas could form. Hopefully someone else can be more helpful.

 

Hmmm, eggs sounds like snails, and the smell sounds like dead snails.....Do you know your water parameters? If there is ammonia, then something has died.