Possible costia

Question
Hi!

I have recently bought a new Ryukin to add to my goldfish tank. The tank is 38 gallons housing two orandas.

I quarantined the ryukin and salted the tank up to 0.2% and did 4 rounds of prazi. This is the usual QT I do on new fish. Sadly, after QT and introducing the ryukin, he became ill and symptoms led to a suspected internal bacteria. (QT tank is 10 gal)

I quarantined him again and salted to 0.2% for one week as well as feeding him home made gel food with metronidazole at the correct dose. As my qt filter was not cycled, I was doing daily 100% changes matching pH and temp, so I stopped salting. In the last three days after making a near full recovery he relapsed. He is clamped, has red fins, and also a red rash with excess slimecoat. I am going to do a 3% bath tomorrow for 5 minutes (watching him) to strip the slime coat, then put him back in the water double conditioned with prime and do a full water change a few hours later.

I am still doing daily 100% changes as they are needed to keep ammonia down at 0ppm. I use seachem prime, and that does keep the fish safe from ammonia forming in between water changes.

To clean the tanks I use a python, however I do not disinfect the hosing so I have potentially spread the suspected costia to my betta tank, goldfish tank,  and my tropical tank. I can treat the goldfish tank with potassium permanganate if need be, however the issue is with the tropical tank as I have a snail and 4 corydora catfish. My bettas (one in the community tank with the corys and one on its own) cannot tolerate anything over 0.1% salt.

Do you have any ideas I could treat the tropical tanks with that should kill costia?

Thanks :)

Answer
Hi Alexander,
Sorry to hear all the trouble you've been through with your Ryukin! I hope I can help shed some light on this...

One thing I am concerned with.. Are we certain this is Costia?
As you probably know, Costia is a parasite that is best diagnosed via a skin scraping and looking at a sample under a microscope. And even then it can be tricky! True, these parasites can cause irritated areas on the fish's skin and cause the poor individual to scratch and itch himself constantly. But these parasites are more common in pond fish.

Not saying its -not- possible this is what your ryukin is dealing with. But symptoms like clamped red fins and a red rash with excessive slime coat plus given the fact he is living in an uncycled tank and being slammed with salt treatments and medications --- if Costia was never mentioned I would immediately point to the simple fact that he is -REALLY- stressed from harsh treatments. Ryukins, like most fancy goldfish, are very sensitive to even small amounts of ammonia and even trace amounts can cause reddening of the fin-rays and distress to the fish's overall system.

If this were my fish. I would be very willing to pretend Costia was never a worry in the first place... And try to just keep this poor guy in as clean water as possible with no harsh medications or salt treatments.

I know you mentioned he had a suspected internal bacterial infection. And I feel his system has been weakened and stressed from that alone plus the damaging effect of ammonia he is dealing with now. Ideally, I would like to see how he would fare in an established healthy aquarium with no more treatments or ammonia problems.

What I'm basically getting at is I see a fish that is showing symptoms of an environmental issue versus an actual disease/infection that needs harsh treatment.

For more goldfish help visit this great website -
http://www.thegab.org

*Let me know how he is doing!

I hope this helps and good luck!
Susan~