Here's the latest scoop:
After cycling the tank for ~4 weeks, all levels tested good. I stocked it with a betta and an oto after the first week of cycling to help jump start it. I went to Petco last Friday and picked up 3 cardinal tetras and this is when the trouble started. The CTs kept dying, so after taking them back and getting 3 more, I was left with only 3 alive. Before the second to last one died I noticed it's tail started to become discolored and turned almost a white color. The entire tail was gone after a matter of a day or less. I managed to take a pic of it (middle one), but it's not a very good one.
That one died and I was left with 2 healthy looking CTs. That was up until this morning when I checked the tank and found that only 1 was left. And even worse than that, I noticed my betta, who was completely healthy and happy the day before, was very sickly looking. I snapped a pic of him too.
I really want to save the betta and the other 2 still alive before whatever it is that's killing them take a toll on my entire livestock. I took in the betta along with some tank water for testing. The levels all look good, but they think the betta has a fungus, so they gave me Pimafix (won't kill my plants) to treat the fungus outbreak.
The betta is not doing well. He is just laying pretty much face down in a crevice in the drift wood and is literally missing nearly his entire right fin. He's still alive, but barely. Should I turn off the filter for now to let the water current calm down and hopefully make it more peaceful for the betta? What is going on with my tank?!? Is it a fungus? Anyone experience anything similar? Advice?