Where to start on tank after fish died from a parasite?


So 2 of my 4 oscars died in my 130 gallon aquarium. My common pleco is still in it and seems fine. My largest oscar I removed three days ago as he was the only one not showing any symptoms of being sick. He is in a 20 gal. Quarantine tank right now mad as heck. My other oscar is showing signs of parasite and I'm removing him and putting him in a 5 gallon quarantine tank. I was going to pull my pleco and put him in the 20 long with the seemingly not sick oscar. Keep in mind I've been treating my whole tank for two days with apI general cure. And have more meds on the way. So far no improvement in the sick ones. Just when they start swimming around and I think they are better they die!

Now my question is, how do I go about restarting my tank? Do I drain and restart? Is there a chemical I can run through it for a few days and then drain and restart? Do I have to pull everything and boil/scrub/dry out for days? Empty everything and recycle the whole tank? What about bio wheels and bio balls and ceramic rings? Never had this happen. Not sure what to do. I fed them feeder fish though. It's my fault.

Correction 3 of 4 oscars died. Sad day for me. Fourth is still showing no symptoms of being sick and still being kept in 20 long quarantine. Common pleco going by himself in 5 gallon quarantine. He shows no symptoms either. 130 aquarium is empty. What now?

maggie thecat

Do you know what parasite you're dealing with? You could treat the entire tank volume with medication, following the interval instructions so that any unhatched eggs or intermediate forms are killed, doing the appropriate water changes along the way.

Or you could nuke your tank, tear it down, replace the substrate and filter media and recycle the system.

Let's see what others think.


Agree with maggie thecat, it'd be very beneficial to know exactly which parasite you're contending with.


Well I sadly did an autopsy of my last fish to pass. He was filled with white looking worms. I had posted a thread asking for help with meds and did the apI general cure. I had to order the praziqu separate as no lfs had it. It's still not here. Supposed to be here tomorrow. This all happened in a matter of 5 days.

I just don't want to overreact and do a bunch of stuff that can be avoided. I figured I'd ask thinking I'm not the only one that's went through this. And the last two years of my hobby this forum has gave me the most help I could ever ask for. A lot more than any person working at any lfs. This is a pic of the white wormy poop coming from him when 1 of the sick was alive.


Did you happen to get a picture during your necropsy?


No I didn't want any memories of my friends autopsy. I was quite disturbed and disgusted doing it.

That's all the whitish wormy poop that came out of the last two overnight. They both died this morning


hampalong may be able to help.


Hello Nick...

Too bad about the Oscars. It was the feeder fish diet that likely got them. Feeder fish are typically poorly cared for and carry parasites or disease. As you know, Oscars are real waste producers and large daily water changes are normal upkeep for cichlids that can exceed 12 inches.

Once you're up and running again, a diet of pellets and sticks made of low phosphate flaked food is good. Freeze-dried krill, earthworms and crickets from your garden will add to the variety.

Good luck.



Yeah I didn't know about the feeder fish being so bad. I do now. Had 3 of the 4 fir almost two years and we're in perfect health til I fed them feeders. Never again. Any suggestions on how to start over? I have read about bleach. Medication bombing it. Tear down and dry everything out. What about driftwood. It's way too big of pieces to boil. They were given to me a long time ago from an established health aquarium. Can it hold any disease?

maggie thecat

Okay, since that's definitely worms, what I would do is this.

Assume your remaining fish is infected.

That being the case, I would return him to the main tank.

I would worm the tank, being sure to follow the instructions exactly, including a reworming four days (or whatever interval the package says) to kill any worms that were too young to be affected by the first treatment.

I would also tear down or treat the Q tank, because the Oscar in there has more than likely passed eggs.


I've been treating the Oscar in quarantine with apI general cure now two days. Get gets another dose in a few hours. Could I not continue to treat him in the small quarantine tank. He is missing his big tank but it isn't like he can't move in the 20 long he is in. He is 5 inch so idk. He just hasn't had any symptoms in the 5 days since this break out. I'm scared to put him in the big tank again til I can get rid of all worms in the tank. I don't mind continuing to treat big tank too or even overdosing it while it's empty and waiting a while before changing water, putting new carbon in and putting a fish in it.

Worms can't live long without a host correct? So if no live life I'd in it, with meds will they go away or die off? How long should that take? If it's about the same time as 4 week cycling it I'll nuke it and recycle it then to be safe. I'm devestated from losing 3 of the 4. I don't want it to happen again. I will never feed feeder fish again!

maggie thecat

It depends on the type of worm, some have intermediate hosts.

You can keep treating with what you're using. If it were me, I would treat in the main tank, but you have to do what makes you comfortable.

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