Hi,
I have a single goldfish in one of my 72 gallon tanks. I strongly suspect he is a carrier of diseases (or that the tank is diseased). Over the years I have used the not-recommend shotgun approach to try to cure him. I have UV sterilizer, do 25% water changes changes weekly (never miss a week!), I also have tried feeding him medi-gold and metromeds, not at the same time, for a period of 3 weeks each. Also I have used praziquantrel, parasite clear, and a few others including maracyn over the last year (again not at the same time).

Whenever I put in a healthy goldfish, I buy one, and put it in a seperate tub for 2-3 weeks to make sure he is healthy, and move him over, the new goldfish gets really sick within 1-2 days. Any ideas what I could do? anyone have the problem before?

I was thinking if its was a good idea to tear down the tank and restart it..

Thanks!

Michael

Wow with all the meds you have given the single goldie it sounds like he is fine. Although he still could still have something that is being passed on. Do you treat the new fish with anything? Do you acclimatise him into a new tank? What are your exact water readings? These are all things that could kill him or he is sick and you have not noticed it, after all goldfish cover there health problems up very easily.

personally i reckon it's the tank. nasty things can really lurk for ages!

In your case, I strongly suspect that there is something lurking there that your current fish is more or less resistant or immune to - something that is not good for "new fish".

If I were you, I would move the single fish into the small "qt type" tank and break down and sterilize the big tank. Nuke the whole thing - blast it clean.

When the tank is clean - the filter.... EVERYTHING - Boil the media/gravel. REplace the biowheel and cartridges - Sterlize the lot - I would then suggest doing a fishless cycle to get it going again.

Be very careful about cross contamination. Remember - it takes less than one drop of water to contaminate an entire tank. Do not share equipment or anything. Wash carefully between tanks.

I bet you will have more success.

Thanks for the replies,

Yes, I use the float for 20 minutes, then drip for 20-30 min method to accclimatize new goldfish. When I get new goldfish, I put him on medi-gold for 2 weeks and check carefully for any sick behavior for 2-3 weeks. I also dump in praziquantrel just in case, since I hear it is fairly harmless to add. Once the new fish moves to the main tank, I usually wash out the tub so any new incoming fish won't be affected.


Water readings:
temp: 72F
PH: 7.1
Ammonia: 0
Nitrites: 0
Nitrates: 2
(just got a new test kit last month!)

The old goldfish seems fine, except he sometimes has some small red veins showing on his tail. I have not identified what the problem is, as I have used every med I have, and he has no other symptoms.

I have a spare 30 gallon tank. I might just do what you said. What is the best way to clean the inside of the tank? I could use something like hydrogen peroxide or something and just nuke everything, but I'm not sure how to make sure it is gone.

Thanks for your advice,

Michael

It is not uncommon for a "static" population of fish to become more or less immune to problems that are in a tank. But what does not bother them may bother a newcomer who has not become "immune". I think that a lot of the myth of fish becoming "immune" to flukes comes from this problem. A static tank of fish will carry a more or less consistent load of flukes. When you introduce a new fish to the tank, the new fish changes the balance of the tank - and flukes may become apparent - on a new fish that just completed qt!

Anytime you add something new or change something, stress occurs and stress allows all kinds of problems that were otherwise held in check to flourish.


This thread discusses sterilization of a tank quite nicely:

http://www.kokosgoldfish.invisionzone.com/...showtopic=41101

Great, I'll try it out, thanks again!