Fish Dying Need Urgent Advie

Seeking a bit of advice on how to proceed with fish tank...

Have an approximatley 200L litre fish tank has been established for past 5 months current stock levels were:

9 Corydoras
3 Dalmatian mollys
12 Neon Tetras
1 Siamese fighter (male)
5 Male guppies
7 Zebra Dianios


Added on Thursday

1 Sail fin Plec
4 Coolie loach
2 Dwarf Gouramis (1male,1 female)

Unfortunatley struggled a bit with getting fish into tank and some of the water from the store got into the tank

Everything seemed ok on Thursday night and Friday, but come Saturday morning found 1 of the coolie loach to be dead at the bottom of the tank with what looked to be cotton wool type fungus over his body also the male gourami on the floor gasping for air. Came back later in the day and found the dwarf gourami in same place gasping for air but also 1 of the corydoras was laying on its side and looked like skin had gone a bluish colour, the Siamese fighter looked like some of his scales had gone white on top of his body and his back fin looked like it had also gone white.

Last night i added some fungus/fin rot medication to the tank with some aquarium salt

Come this morning found 2 more dead corydoras the gourmie had died and alot of the corydoras seem to have developed this fungus.

I have carried out the API water tests for Ammonia, nitrite, PH, Nitrate tests come back fine.

Can anyone shed some light on this and offer advise on how to cure the sick fish and prevent this spreading through tank any further.

It sounds like columnaris to me. The bluish film on the fish could be a parasite.

Any signs of darting, or erratic swimmng, flicking and rubbing.

Chilodonella



Symptoms:

The skin and gills become discolored, taking on an opaque, bluish-white to gray coloration. The area between the head and dorsal fin is generally the most severely affected. In advanced cases skin begins to swell, eventually shredding and falling off in strips. Gills are also affected and may be completely destroyed. Clamped fins, listlessness, hanging at the surface and gasping may also be seen. The fish may rub or scrape against objects in the aquarium in an attempt to relieve irritation.



Cause:

The ciliate Chilodonella cyprini. These heart-shaped parasites, at a size of 40 to 60 microns, are not visible to the naked eye. The parasites are able to swim freely, spreading easily from fish to fish. Reproduction occurs by asexual division.



Treatment:

Highly infectious and able to kill in great numbers, Chilodonella may very well be the most dangerous skin parasite there is. Overcrowding increases the risk of infection. Acriflavin Plus, Malachite Green, Paraform, Quick Cure or Formalin are the drugs of choice for Chilodonella. All fish as well as the aquarium they inhabit should be treated.


A link to columnaris.
The scales can go white on the edges or white with columnaris aswell.
http/www.flippersandfins.net/flexibacter.htm