Treating internal parasites

Hey all,
Just the other morning one of my guppy fry passed she was about 4 months and looked a little bloated for about 2 weeks prior to her passing.
This morning I picked out 4 other fry all about 2 mo. that were acting a little funny. 2 of the 4 were unable to really get off the bottom of the tank. They scooted around on their bellies to get from place to place. The other 2 were swimming around but not using their back ends nearly as much. As a result they were working a lot harder to swim and when they surfaced their body was more vertical than horizontal.
I figure that the fry are showing symptoms of this first since they are younger and smaller and overall more susceptible.

My tank contains guppy (fry and adults), Pristella tetra, and a raphael cat.
I think this is a case of internal parasites, however I am unsure.
I feed NLS Thera A (non-medicated anti-parasitic food). I'm hesitant to use any sort of true medications because of my Raphael cat (even at half dose).

First of all, does this even sound like internal parasites, or could I be dealing with something else?
Secondly, is there any other way to treat parasites without using meds or are there medications that are definitely safe?

 

I've heard the way to treat a bloated fish without medication is to feed a pea. Not sure about the internal parasites though.

 

I've heard the way to treat a bloated fish without medication is to feed a pea. Not sure about the internal parasites though.

That's for constipation, not for parasites.
The mentioned symptoms aren't pointing towards internal parasites though. But I could e wrong.

 

There's been a lot of white stringy excrement I've noticed. I got some API general cure stuff from Amazon. I'll soak their food in that as well as some garlic and treat for about a week.

The guppies are the only ones showing any sort of symptoms. Tank perams tested today were normal; 0/0/20

 

Hello

What is a best way to treat internal parasites in your aquarium. Should you just quarantine and treat sick fish or should I treat the whole tank. Are internal parasites contagious?

Thanks

 

Yes, internal parasites can spread, and I suggest you quarantine the fish that have it(if most of your tank already has it, I see no point to quarantine if only 1 or 2 fish look fine, as they will be in an environment damaged from the internal parasites), and medicate them. There are quite a few good medications out there.

 

There are several different types of internal parasite and they react to certain medications differently. What are the symptoms you are trying to treat? What species?