Treat display tank for protozoa?


Fish Fanatic
Sep 15, 2021
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Santa Clara
Hi, I had two mollies in my 10 gal tank under metro+food treatment.
And i got the new 20 gal as a display tank, cycled it all, and since I didnt have a third tank to use as a quarantine I got my new two mollies and one platy in the display tank. They were fine in the display tank.

When I finished the metro and food treatment in my 10gal tank, my fish got a little better in terms of internal protozoan parasite. But I noticed that the tank was crashing and no matter how many water changes I did, or use water conditioners, I just couldnt save the tank. (This is my first tank as an adult.)
So I moved them to the display tank. Eventually one died because she was already so sick when I first got her :(

So I now have four fish in my new 20 gal tank. The fish seem fine except for the occasional clear stringy poo! I think my old fish spread it to other fish.

I want to use paracleanse but I dont want the display tank cycle to be affected. Im more afraid because on the back of the paracleanse it specifically says that the medication can cause harm to beneficial bacteria.

Should I move the four fish (i dumped everything out from my old tank and cleaned the whole thing to make it a hospital tank.) to the hospital tank, and treat them with paracleanse?

What about the bacteria that is already present in my display tank? Can i do big water changes to get rid of them while my fish are in treatment?


Fish Guru
Jan 26, 2008
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Perth, WA
The most common cause of stringy white poop in livebearers like guppies, platies, swordtails and mollies, is intestinal worms like Camallanus and Capillaria. Tapeworm are also commonly found in them.

If the fish are eating well but doing stringy white poop, then the problem is most likely worms. See section 3 of the following link for information on intestinal worms in fish.

Bruce Leyland-Jones

Fish Aficionado
Jul 1, 2021
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Cleator Moor, Cumbria
What about the bacteria that is already present in my display tank?
Beneficial bacteria would survive for quite a long while away from the tank, especially if kept wet.
You could place filter media, any removable decor and even some substrate into a separate container. This would keep it safe and you could return it after any treatment. Ideally, it would be kept warm, but even if left cold, the bacteria would simply enter a dormant phase.

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