Dying Pygmy Cory

[CrazyDiamond88]

Hello. The past month or so I've had about 3 pygmy cory die on me.
 
My water stats are fine when I check.
 
However I used to have a betta fish in with them and I think he was stressing them out.
I took him out about 2 weeks ago after I had 2 cories die. 
 
Anyway another cat has died since the betta moved out.
 
The symptoms are that the cory will sit away from the others, often at the front of the tank. Fins are clamped. It's colour is really dull - almost completely white. Sometimes the cory will lie on its side or in an awkward position. Then the cory will get really thin and clearly it has not been eating. Then one day I'll find it dead.
 
The 3rd one died yesterday.
 
Now another one is looking poorly and I'm really worried.
 
I want to know, should I medicate? I have some med which is an all purpose anti fungal, anti bacterial and anti parasitical thing. But the cory are in the tank with shrimp and I think the med will harm them.
 
I have the betta tank which I am currently treating for ich with that med. Could I put the cory in with the betta? I could maybe divide the tank up or put the cory in a breeder box...
 
I just really need some advice, I am so frustrated and upset about losing my fish.

 

[KirkyArcher]

I know people will scream and shout about this but try adding salt, I've added API aquarium salt to both my tanks  containing various species of corydoras and not one has ever suffered any problems people say that salt will cause them, and it's invert safe too! and you can safely add the likes of melafix and primafix with the salt now that your betta has been removed
(1 tablespoon for every 20L of water or half dose that if you have vallisneria or any very fine leaved plants in your tank)

 

[CrazyDiamond88]

Thank you Kirky I appreciate your response! 
 
Should I add all those things? Maybe just to be safe? 
 
The prospect of beating this illness is so exciting x)

 

[KirkyArcher]

Yes give it a shot, and like treating with most meds get an air stone going in there or at least adjust filtration for more surface agitation.

 

[CrazyDiamond88]

Okay I will do all of that, thank you!
 
It may have to wait till Tuesday though Hope that he hangs on.

 

[KirkyArcher]

You could add regular table salt as it is an emergency, @ 1 teaspoon per gallon

 

[CrazyDiamond88]

Hm, I have table salt but it has anti-caking agent.
 
I also have sea salt, could I use that instead? 

 

[KirkyArcher]

sea salt will be the best option, even the panic over using salt with anti-caking agents or iodine is unnecessary!

 

[CrazyDiamond88]

Okay thank you! I will do that right now!

 

[KirkyArcher]

Fingers crossed things haven't advanced too far and the poorly little fella pulls through. Don't forget to aerate best you can.

 

[CrazyDiamond88]

Thanks so much for your help and support

I am now noticing that the Cory has worn down barbels. The healthy ones do not.
I read that is because of bacterial infection.
Apparently one of the causes is a dirty substrate. Now am I getting worried because I very rarely vacuum my sand. I find it very difficult to do and especially with all the plants in the way.
Maybe I should get a mechanical one. That would make it easier I think.