How long do parasites survive in fish-free water?

[SimonW]

Hello friends:

I have unfortunately developed a kind of fish parasite-phobia. I just cannot stop worrying about fish parasites. Now the following question bothers me most:

I moved all my koi inside this October when the outside pond water has dropped to 10 centigrade, and I will probably not move out the fish to the pond until June 2021, when the water temperature has reached 15 centigrade. I wonder whether it will be parasite-free after a so long fish-free period?

I am most concerned about gill fluke. I heard that gill fluke produces tough eggs, but once they have hatched the juvenile gill fluke only can live 1 or 2 days without a fish host. I hope that they all have hatched and died then.

Thanks!

[ademink]

Parasites are essentially always present in ponds in small numbers and become a problem when fish become weak due to poor water quality, introduction of unquarantined fish, etc. Parasites are fairly easily treatable. Have medications on hand to treat parasites, should you have an issue come up:
-Fluke-M or Praziquantal
-An product with formalin and malachite green
-Dimilin X or similar

Store them properly, address issues if they come up and enjoy your fish.

[KTownKoinut]

I've had koi for years, man....and never once had probs with parasites!! Don't waste time worrying about it....it'll give ya wrinkle lines and grey hair for nothin!!!

Just keep your water healthy, and the fish will take care of them selves!!

[SimonW]

Andrea and Koinut:

Thanks!

I have good trust in formalin-malachite green and potassium permanganate against parasites, and I will not hesitate using them. But I am restrictive with the use of the other medicines which seem to be antibiotics, because I am worrying about the parasites developing resistance.

This summer I got a parasite outbreak without deterioration in water quality or introduction of new fish. Probably due to stress caused by netting and moving my koi to outside pond.

[RichToyBox]

The pond will most likely be parasite free by then, but... All fish have some parasites all the time. The numbers remain low and of no concern until the fish are exposed to some form of stress, whether major temperature changes, chemicals, major pH shift, high ammonia, high nitrites, .... and then the weakened fish can be overcome by a major population explosion of the parasites. Even if the fish and pond were parasite free, I know of one person that went to the trouble of doing a scrape and scope on a frog and found it to have some of the parasites we fight when fish have problems, so parasites will find themselves being brought into the pond.

[KTownKoinut]

Dang!!! Ya mean I gotta add Frogies to my 'hit list', along with Coons and other such vermin!!!!??? Oh well!!! Where's my ammo!!!???

[SimonW]

Thanks all!

Obviously I cannot keep my koi pond parasite-free, but that is still very interesting when I am trying to keep my aquariums parasite-free.

I have several aquariums but only one is used for 2 fry from this year. One of the fry seems to get parasite infection, so I took both out and dipped them in 50% NaCl for 30 seconds, then I moved them to an other aquarium that had been fish-free for months. So I guess that they are parasite-free now.

The first aquarium will be fish-free for at least 2 weeks before I move the fry back there again.

I think that I have found the perfect way to fight parasite infection in the future: When my koi are infected I will dip them in 50% NaCl for 30 seconds (small koi) to 2 minutes (bigger koi) and then put them in a quarantine tank that has been fish-free, and keep them in it for at least 2 weeks. Meanwhile I let the pond be fish-free for at least 2 weeks. No complicated procedures or medicine is needed.

[ademink]

Curious what you mean when you say one of the fry seems to get a parasite infection. Are you scraping and scoping or what is this based on?

[SimonW]

Hello Andrea:

Thank you for your quick reply!

It is too small to do scraping. I made the guessing based on the symptom: Fuzzy areas with slim on its body, clamped fins, and long periods of resting on the bottom. Quite similar to the symptom my koi showed this summer when they got fluke/costia/chilo outbreak.

I have been much interested in the dipping-in-NaCl-solution method, so I just took the chance to try it out. Seems to be very successful: I did it for 3 days ago, and today both of the fry look happy and healthy in the new aquarium.

I must mention that the fry with symptom got fungi infection (thread-like white fuzzy things on its infected area) the day after the 50%-NaCl-dip, so I dipped it in 40 ppm malachite green. Maybe it is this malachite green-dip, not the 50%-NaCl-dip that rescued it!

[kdh]

Thanks all!

Obviously I cannot keep my koi pond parasite-free, but that is still very interesting when I am trying to keep my aquariums parasite-free.

I have several aquariums but only one is used for 2 fry from this year. One of the fry seems to get parasite infection, so I took both out and dipped them in 50% NaCl for 30 seconds, then I moved them to an other aquarium that had been fish-free for months. So I guess that they are parasite-free now.

The first aquarium will be fish-free for at least 2 weeks before I move the fry back there again.

I think that I have found the perfect way to fight parasite infection in the future: When my koi are infected I will dip them in 50% NaCl seconds for 30 (small koi) to 2 minutes (bigger koi) and then put them in a quarantine tank that has been fish-free, and keep them in it for at least 2 weeks. Meanwhile I let the pond be fish-free for at least 2 weeks. No complicated procedures or medicine is needed.

Could you explain this formula a little better for me. I ain't a smart person.

[SimonW]

Could you explain this formula a little better for me. I ain't a smart person.

This formula is my own :-)

I got this idea from Richard RichToyBox. He wrote once in my thread that he had seen commercial fish farmers dip their fish in saturated NaCl before the fish were thrown into the growing tanks as a preventive measure against possible external parasites.

I had also read that one could give parasite-sick fish dip/bath in NaCl-solutions with various concentrations, ranging from 2% to 10%. Then I thought: I am bolder, but not as bold as the commercial fish farmers, so roughly 50% of saturation (which means roughly 200 gram NaCl in 1 liter water) would be nice to start with, and I decided to go for 2 minutes for fish including koi bigger than 40 cm and 30 seconds for small ones.

Since this summer whenever I am afraid of external parasites on a fish I give it a 50% salt dip. No obvious problem has been observed so far for fish that were healthy before the dip. I have not tried this method for parasite-sick fish (haven´t got any since I got the idea) until this time for this small fry, and obviously it got fungi infection afterwards. On the other hand it had heavy symptoms (>50% of its tiny body were covered with slime). I will continue to test this method.

[kdh]

I'm pretty sure your koi well not like this.

[SimonW]

I'm pretty sure your koi well not like this.

Obviously. They turned belly up within seconds. I will not try this on my more precious ones until I have got 100 problem-free cases.

[kdh]

Obviously. They turned belly up within seconds. I will not try this on my more precious ones until I have got 100 problem-free cases.

Obviously?

Kinda contradicts your last paragraph post 11?

[SimonW]

Obviously?

Kinda contradicts your last paragraph post 11?

You asked me whether my koi disliked the treatment, as if they have feelings. My answer to this question is yes, if they have feelings. Not said that the method is bad.

And none of the fish that I have tested this methods on are precious to me :-)