Guppies dying one by one

SamGuppies · Nov 8, 2020

Hello,
I am new to the fish world. I have a 20 gallons tank with 10 pregnant guppies, 2 male guppies and 4 mollies with live plants and drift wood. I noticed my guppies are slowly died one by one. I did weekly 10-20% water change. I notice their tail looked darker and swollen. I am not sure what it is to properly cure it. I tried 2 tablespoons of salt to the tank water. Not sure what else should I do now... anyone have any ideas what I should try now? I moved the guppies with the weird tails a quarantine box just in case they are contagious.

Flyfisha · Nov 8, 2020

Hi SamGuppies,
I see on your profile you are still learning of the nitrogen cycle. It’s highly likely this is the issue. Unless you added ammonia to the tank for 6 weeks before you added fish the tank is not cycled. / the tank has no good bacteria .
Do an immediate emergency 40% water change NOW and replace with temperature matched conditioned water.
Then you can ask about and we can all help you become more familiar with the nitrogen cycle.
Right now it’s a small water change needed.

Do you have conditioner / de chlorinator?

SamGuppies · Nov 9, 2020

My tank was set up at least 10 months ago so I think it is pretty established. I used Seachem Prime Fresh and Saltwater Conditioner each time I change out my water. I do have a heater for my tank. The temperature is set at 77 F.

Flyfisha · Nov 9, 2020

Do you have nitrates in the tank water? As you change 10% -20% water each week I wonder if part of the issue is high nitrates?

Do you know the GH General hardness , the mineral content? Guppies in particular will not last long in low mineral water.
While a soft water fish can make do with hard water the opposite is not true . Guppies need around 150 ppm GH.

The weird tails is something I am unfamiliar with.

Queasy · Nov 9, 2020

Guppy in the second picture has columnaris. Remove any fish that have that darkness/fungus looking stuff on them immediately to a different tank. This usually wipes out your entire tank within 48 hours. I wouldn't bother with any medicines because most of them don't treat bacterial issues. Even if you were to get your hands on a bacterial medicine, it'll wipe out your BB and kill your fish anyway. Best of luck. Act fast and hope for the best.

SamGuppies · Nov 9, 2020

Queasy said:
Guppy in the second picture has columnaris. Remove any fish that have that darkness/fungus looking stuff on them immediately to a different tank. This usually wipes out your entire tank within 48 hours. I wouldn't bother with any medicines because most of them don't treat bacterial issues. Even if you were to get your hands on a bacterial medicine, it'll wipe out your BB and kill your fish anyway. Best of luck. Act fast and hope for the best.

SamGuppies · Nov 9, 2020

Thanks! Yeah, I noticed the infected fish will die in a couple days after I noticed the tail start swollen up and turn white no matter what try to do.

SamGuppies · Nov 9, 2020

Flyfisha said:
Do you have nitrates in the tank water? As you change 10% -20% water each week I wonder if part of the issue is high nitrates?

Do you know the GH General hardness , the mineral content? Guppies in particular will not last long in low mineral water.
While a soft water fish can make do with hard water the opposite is not true . Guppies need around 150 ppm GH.

The weird tails is something I am unfamiliar with.

Thanks! Good to know because I never pay attention to the GH & KH when testing the water.