Can’t add any new fish without them dying

Hello all,

I have multiple tanks (2x20 gallon) and (2x10 gallon), and in one of the twenty gallons I would like to add another Balloon Belly Molly. I have tried adding 3 over the course of the last couple months, but all the new ones die within about a week. The tank has 2 mature female ballon mollies, and 2 lemon eye tetras, as well as a Rubber Lip Pleco. I’ve been told I’m still able to add another Molly without it being crowded. All levels are normal and whenever the fish is added they are acclimated to the new tank properly. Any help on why the new ones are able to survive would be helpful.

Please provide your test results for nitrate, pH, nitrite and ammonia, also your maintenance/ cleaning routine. "Old tank syndrome" and uncycled tanks cause deaths.
Where do you buy the fish that die? Some stores don't have good quality fish.
Finally, balloon fish have poor health because their short bodies squash their organs. They are best avoided.

Naughts said:

Please provide your test results for nitrate, pH, nitrite and ammonia, also your maintenance/ cleaning routine. "Old tank syndrome" and uncycled tanks cause deaths.
Where do you buy the fish that die? Some stores don't have good quality fish.
Finally, balloon fish have poor health because their short bodies squash their organs. They are best avoided.

Click to expand...

Nitrate is below 10, pH is in the mid 7’s, Nitrite is 0, ammonia is currently present as the fish just died, but normally it is at 0. Temperature is set at 78-80. The tank has been going for 6 months and is cycled. Ive purchased from Petsmart, Petland, and my local high quality fish store (as I thought maybe the reason for the deaths were the stores, I tried different stores). If all the fish were dying I’d think it’s the tank, but it’s only the new ones. All of the other fish that have been in the tank for the last few months, they have been fine.

The one that passed today had a strange red mark on the body, which makes me wonder if it had been killed by something such as my rubber lipped pleco.

The fish in the picture has a bacterial infection

don't buy balloon fish because they have heaps of health issues, shorter lives and often suffer during their lives due to short bodies and squashed organs.