Confusing deaths

[PhantomBold]

I have a 5.5 Gallon shrimp tank that had about 12 cherry shrimp, 1 amano shrimp, 1 asian stone catfish and 1 scarlet badis . About a week ago I started having some deaths. 3 of the shrimp randomly died and I couldn’t find any reason why. A few days later so did the asian stone catfish who had all been fine in there for a month with minimal changes in tank parameters. My LFS sells them for cheap, so I decided to try another asian stone catfish. Within a few days the second one died. This time it turned white with bright red around the cheeks and underbelly. The only change I could find is 3 weeks ago I had put in some java moss that had introduced some microorganisms. I’ve identified cyclops, seed shrimp, detritus worms, limpets, nematodes, and bryozoan. I’ve read that although pests, all of these should be harmless to the fish and the badis loves gobbling them up, which he does. I have used some seachem flourish before but in smaller doses than recommended. I use a sponge filter and sand substrate. I have java moss, betta moss bolls, and Christmas moss. As well as drift wood.

Ammonia: 0
Nitrite: 0
Ph: 8.2 ( ik high )
Temp: 72
TDS: 220
Copper in florish > 0.0001 copper sulfate (guaranteed invert safe)

 

[coralbandit]

Do you know your nitrates ?
How often do you change how much water ?
The quick death and symptoms of second stone cat would indicate a water quality issue IMO .
What is the TDS of the water you use before you add it to tank ?

 

[PhantomBold]

Do you know your nitrates ?
How often do you change how much water ?
The quick death and symptoms of second stone cat would indicate a water quality issue IMO .
What is the TDS of the water you use before you add it to tank ?

Nitrates are 5ppm I change 15% of water every 2-3 weeks because it’s an under stocked shrimp tank with 2 tiny fish making most of the waste. The TDS of the water I add beforehand is 16 it’s reverse osmosis.

 

[absolutangel04]

For what its worth, my experiences with Asian stone cat from multiple sources always include random deaths. They seem to come in either predetermined to die within a couple months, or to be the hardiest fish alive and live forever. They also need highly oxygenated water in order to thrive.