HELP! - My tiger barbs keep dying

[onewayticket]

Hello every friend,

I have a 55g planted aquarium with 5 mollies, 5 platies, 3 catfishes and 1 algae eater. The tank is quite stable. I put 4 tiger barbs (2 males, 2 females) last Thursday. Last weekend, I was out of the town. When I came back home at Sunday night, I found one tiger barb died. In the next morning, another one died. Now I also find the third one is not normal. It drifts along and has its belly upward. Although it's still alive. It looks it's dying. What happened with them.

Please help me. Thanks in advance.

 

[Brookster123]

How old is the tank?

 

[onewayticket]

I set up this tank 6 weeks ago. I thought the cycling was done, so I started to add some more fish. The other fish including platies and mollies have no problem with water. They look happy. Although it looks stable, I still keep adding API AMMO LOCK regularly.

 

[Brookster123]

Have you been testing your water?

 

[onewayticket]

Because of the AMMO LOCK, the test result won't be accurate. So I didn't have the water tested recently.