all of my fish are dying :(

[rsh]

I've had fish for a year now, and my first fish died after 5 months from dropsy, and then my other two died months later from what im assuming is old age. I've always had seemingly healthy fish and some just pass (as fish do), but over the last few weeks ALL of my fish have died. Like 30 fish in 2 days. 

29 Gallon Tank: (had platys, cherry barbs, mollies, guppy- now has 1 angelfish, 2 mollies, 1 guppy)

My water has tested normal every time I've tested it (which has been like 5 times, and a fish store has also tested it and said it looked good). I changed the water and added 7 new fish and 3 died in 3 days. I just replaced my filter in the tank (was time to change it) that had the 30 deaths.

5.5 Gallon Tank: (had 1 male betta)

Today, I noticed the fish had a laceration on its side that had fungus coming out of it so i gave fungal meds and bacterial meds and he died today. 

I'm kind of at a loss. I went from raising baby platys and having a thriving tank of 30 fish and a playful betta, to a tank with 4 fish and an empty tank now. I have heaters and filters in each tank, I clean them regularly, the water is testing normal (including ammonia) and my fish are still dying left and right. What am I missing?

[Tony s]

Wow, ok, sorry for your losses. If they’ve been with you for a year. Was there anything that changed. Hard scape, cleaning tools, dechlorinator? Or was it all stable?  Did you get your water parameters when they started dying? Sometimes that’s the most important thing to do. It can tell you what’s going on. It’s possible, when you got new fish, something was introduced like a parasite or infection. Or you had something going on before that caused the loss of the new fish. (I’ve had that before, unfortunately) That would account for the one tanks crash. The betta may not have even been related to that. Or, it could have been transmitted tank to tank via cleaning equipment. (I’ve also had that before). Plates are usually very hardy. So it’s very possible something was introduced.

[rsh]

in the 29 gallon, i had recently introduced 2 new fish and then a week later the 30 died, so i suspected a parasite or infection so that makes sense. I cleaned the water though and there was no crossover between the first 30 and the new 7 and 3 of the 7 have died as well for reasons unknown. I tested the water every time a fish died and it has been normal each time.

in the 5 gal, i cant think of anything that couldve been transmitted tank to tank but i easily could be forgetting.

 

i really appreciate the help! thank you!

[Tony s]

They may have adjusted the chlorine levels in your water as well. Platys are usually hard to kill 

[Colu]

Mast die off is usually caused by  a fast moving bacterial or viral infection  or water quality it's possible your water company flushed the pipes leading to a higher dose of chlorine in your water that would mean you under dosed your water dechlorinator have you tested your water for chlorine @rsh