Firstly apologies if this question is in the wrong place in the forum. I got frustrated trying to get this working.
I set up my tropical tank about 2 and a half weeks ago.
I transferred about 8 fish from an old tank, and lost some of them.
I bought 2 dwarf gouramies on Saturday, and they seemed to be getting on fine. Now they are at the top of the tank gasping for breath. The 3 cardinal tetras I bought have now died.
There is obviously something wrong with the water - the PH is fine.