Fish Dying

I'm sorry to hear you've had such a bad start to fish keeping 

It sounds as though the most recent purchases were sick when you bought them despite what the shop said. This is unfortunately all too common.

In the UK, eSHa 2000 is just about the strongest medication we can get. Since that doesn't seem to have worked, the next thing to try is daily water changes - of around 50%. Having a 180 litre tank, I know this is something you don't really want to do. But fresh water often helps fish.
You could also use salt - aquarium salt rather than cooking/table salt as they have anti caking agents added to them. Use at the rate of 1 heaped 15 ml spoonful per 20 litres tank water. Remove some water from the tank and dissolve the salt in that, then pour it back into the tank. At a water change, add enough salt to treat the new water only to keep the level in the tank water constant. After 2 weeks, stop adding salt to the new water and let water changes dilute the salt away.


For future fish, I would get another small tank to use as a quarantine tank. I discovered earlier this year that using plants in a quarantine tank means you don't need mature media. In a 25 litre QT, I used 2 bunches of elodea (bought at the same time as the fish) plus 2 large water sprite plants which I moved from my main tank, and this was enough to keep ammonia and nitrite at zero with 12 kuhli loaches in there.
Leave the new fish in the quarantine tank for at least two weeks and watch them for signs of disease. Move them into the main tank only when you are 100% sure they are disease free.

Most fish can cope with salt for 2 weeks. The dose I gave is the lower dose for fish which can't tolerate much salt - tanks with only livebearers can take double that amount.

Salt should not be used full time because, as you say, some fish can't tolerate it. The majority of soft water will suffer kidney damage if salt is used for longer than a month, and high doses will burn the skin of fish like cories and loaches. But that dose is safe for up to 2 weeks.



Decades ago, salt was used routinely in fresh water tanks and you do see that recommended even now. It is this type of salt use that we tell people not to do.