Platies rapidly dying

[Spookie]

Hello,
I noticed last week one of my fish was acting lethargic/laying on the bottom of his tank and breathing rapidly. I put him in my quarantine tank and it died overnight, but all other fish appeared healthy. Two days ago another of my male platies was acting strangely/pooing white and he was really bloated. I put him in his quarantine tank and treated him with an anti-parasite medication (API) and my boyfriend saw him literally drop dead about an hour later - he swam up to the top of the water and nose dived into the gravel and was gone.Yesterday, another male platy in my main tank got sick and died last night suddenly. Today, a fourth male platy was also seemingly sick/hanging around the heater. I took him out and while he was sitting in a container acclimating to the quarrantine tank's temperature he died in about five minutes.

No fish are acting sick until a day before they die. The main tank is 36 gallons and has mollies, platies, swordtails, tetra, and a pleco (about 25 total). All of the readings are fine, I've been checking all of the ammonia/nitrite levels and they are 0. Nitrates are at 20-25 and have been that way for as long as I remember - I vaccuum the gravel once a week and change the water, and the water where I live is naturally high in them. I did get new fish about a month ago but all are healthy until its too late.

I have noticed that some of my fish have gotten really skinny. They all eat, and I feed them a varied diet often, but yet some are stick thin regardless of eating so much. I would treat the main tank with a parasite medication but I have about 20 two week old fry in that tank and don't want them do die. Any suggestions? Anything to look for?

***Update, today a dalmation swordtail is now acting sick/swimming near the top of the water. He has a HUGE orange/brownish bump protruding from one side of his body (his normal color is white) and his poo is white and stringy. What is this!?

[Spookie]

Here are some blurry pictures

[Lainey183]

Is the red spot on him normal?

[Spookie]

More, his normal side and his infected side

[Spookie]

No, I just noticed the growth when I got home today... it has definitely never been there before today. It literally sticks out from the side of his body.

[Spookie]

I don't mean to pester anyone but today the tumorish bump is even bigger/more red. I'm not sure he will be able to recover, he has stopped eating.

[Lainey183]

Have you tried salt baths?

[absolutangel04]

My best guess in this situation for the growth is a tumor. If it is a tumor, theres nothing you can do about it.
It sounds like you have some sort of internal parasite in your tank that is perhaps being passed from fish to fish. You may have to treat the whole tank with an anti-parasitic. You can also try putting adding garlic to their food. That will help stimulate their appetite and it can help their immune systems if they are fighting a parasite or bacteria.

[Spookie]

Would API General Cure be safe for young fry? I haven't done salt baths only because I'm assuming most of the fish are infected and I would have to do all 25 or so. Should I just add extra salt to the entire tank instead? I would take the fry out to treat the adult fish but they are flashing now too... The only problem with adding lots of salt is that I'm worried it would annoy or harm my pleco/tetra/plants/snails. My biggest concern is definitely eliminating this problem though, especially if a fish is getting tumors somehow.

[absolutangel04]

I don't think adding a little salt to the tank would help anything, and it wouldn't be good for your snails. If it is a tumor, it might be unrelated to the other issue. Tumor-type growths are actually rather common in livebearers. Some potential cancers are linked to some color genes in livebearers. Another possibility is an internal swelling or hemorrhage in response to whatever bacteria/parasite is infecting the fish.
I am not sure if that med would be ok for fry or not. Fry can be rather sensitive. You can try emailing the company and asking them.
You may have remove your snails from the tank anyways depending on whether or not your meds are safe for inverts. I suggest you google any med you consider using to see if it's invert safe.

[Lainey183]

What kind of snails do you have? I would probably try to remove everything that you think might be harmed and treat the tank. You can always put them in a large plastic bin for a short period of time.

[Spookie]

I have little apple snails and little cone snails in the gravel, but there are tons of them. I'll try to take out as many as I can. Should I also try taking out the pleco since he is scaleless? Thanks! I'll start treating the tank tonight. I don't see the swordtail with the tumor, I am pretty positive he has died I hope the other fish improve soon.

[Spookie]

The swordtail did die today Looking closer at his body, the tumor bump became like a huge open hole in his body once he was dead. Im not sure if thats normal, but I began the parasite treatment. Should I also give them anti-bacterial medication sometime? Thank you!

[Lainey183]

I would probably clean the substrate really really well and do a decent sized water change and begin medicating. I would do the salt and the parasite medication.