Several Dead Fish, Intestinal Parasites?? Please Help!!!

I started my first 29 gallon freshwater tank about 6 months ago. I did TONS of research, and made sure to start up and cycle my tank properly. Once my tank was cycled, I bought 6 zebra danios and let them sit for 2 weeks. They did fine. I purchased more fish, they did fine too. Then I had a round of Ich, and lost a Bristlenose Pleco. I bought another one and it died the next weekend. Bought a third one about 2 months ago, and it did fine until about 4 weeks ago when it started having a bloated belly and white, stringy poo. I lost it after two weeks of that. I tried to treat it with stuff I had on hand and it didn't work. A week later, I lost 2 gold dust mollies. When I found them dead, they both had very bloated bellies, and had been acting weird for a few days, and I had thought nothing of it. Then, the other two started acting weird last week. I lost one of them yesterday, and the other today. Below is a picture of the one that died today. That is what all of them looked like when they died. A few things that AREN'T the problem:

1. Water Parameters. I tested them this morning, and they were all fine
2. Overstocking. The highest amount of fish I have had in my tank at once is 16, 10 of which were tiny zebra danios.

A few things I am doing right now/tonight

1. 50% Water Change
2. Cleaning Walls/Gravel
3. Trimming my plants (They need it.)
4. API Melafix (one of my fish is prone to fin issues and is having some right now.)

What should my next steps be? I appreciate any wisdom you have to give. Thanks so much!!

TheFishMan2021

how big is your tank
i think it is dropsy, melafix works fine for me

params?

I have no idea what this could be. Might be internal parasites but I am not an expert. I’m sorry about your fish.

Sgooosh said:

how big is your tank
i think it is dropsy, melafix works fine for me

params?

Click to expand...

Thanks for your help

P.H. 6.6
Ammonia 0ppm
Nitrite 0ppm
Nitrate 20ppm

TheFishMan2021 said:

Thanks for your help

P.H. 6.6
Ammonia 0ppm
Nitrite 0ppm
Nitrate 20ppm

Click to expand...

this isnt the most important some poeple could argue,
but livebearers like moly sholuld not be in such low ph water. it makes them weaker.
your params are fine,
did you add anything or do anything recently

Sgooosh said:

this isnt the most important some poeple could argue,
but livebearers like moly sholuld not be in such low ph water. it makes them weaker.
your params are fine,
did you add anything or do anything recently

Click to expand...

Ok, that's a good point. I haven't added anything or done anything special recently, but Dropsy makes sense because before they died they would just sit at the bottom of the tank for a week or so. I now have a large Black Skirt Tetra who is having similar behaviors, so I'm thinking I will put it in a quarantine tank. Do you have any good medication recommendations for dropsy?

I hate to disagree but Dropsy doesn’t affect a group of fish as it s not contagious. However, as a symptom of another condition, it can be parasitic or bacterial which could affect other fish too. Your profile doesn’t indicate if you are in the U.S. If so, you can try Prazi Pro for internal parasites. Furan-2 is good for bacterial infections but don’t use both together.

It sounds like, especially with the white stringy poo, that intestinal parasites may be blamed here. If you do not have live plants, snails or scaleless fish I would recommend treating the tank with CopperSafe - it will kill any larvae stage parasites in the tank.

As far as treating goes, in the U.S. the best bet is to order Prazi Pro or order Metronidazole (mixed with food) to treat. Typically, by the time that you notice the worms to the extent you are describing, it can be tricky to save them. Once the worms leave their body the fish is susceptible to secondary intestinal infections.

Best of luck!

What’s the Gh of your water supply ? What temperature is the tank currently at ? And do you use an air stone or even an external filter ?
May be an oxygen issue ?
could we get a photo of the full tank ?