100% water change - how long before adding koi back in?

[Alanw]

My 1900 gallon pond had too many leaks in its 10 yr old PVC liner to patch, so I drained it & installed new EPDM liner. Koi are in a 200 gallon stock tank meantime (4 18-20" adults, 4 6" offspring). I've refilled, de-chlorinated, including chloramines, and begun bio-filtration with UV. How long before I can put the "family" back in?
Thanks, I'm glad I found this forum, and hope this isn't a repeat question!

 

[sissy]

should have saved the pond water .Is it well or city water because now it may take longer before you can add them back .

 

[Mucky_Waters]

To make sure they aren't stressed when you introduce them back into the pond you want to try and get the temperature and PH as close as possible to the water they are currently in.

 

[MitchM]

Do you still have the old filter media?

 

[Alanw]

Thanks all. The 200 gallon holding tank has old pond water, & I'll add that back in. Using city water & temperature should be about the same. I can use a couple of "disposable" young ones to add bacteria before putting the adults back in??

 

[MitchM]

I'm not in favour of using sacrificial fish for cycling a pond, use straight ammonia instead.
Turn off the UV until/if it's ever needed
You need an established nitrifying bacteria population before the pond is ready for your fish. That will take time.
If you don't have old filter media, you will need to run your pond and add in some viable nitrifying bacteria.
Monitor ammonia and nitrite levels until they both read zero.

What are you doing for filtration for the fish that are in the holding tank?

.

 

[Tula]

When my current pond was built, I added my koi right away. The water was treated with Prime, I'd saved some of the old pond water and restarted the filter. I tested the water regularly .

 

[Mucky_Waters]

If you have a limited number of fish that are surviving in a 200 gal stock tank there should be absolutely no need to pre cycle a 1900 gal pond before adding those fish, that extra 1700 gallons gives you a huge safety buffer giving plenty of time for the pond to "cycle" itself before the fish could ever produce discernible ammonia levels in a pond that size.

 

[Meyer Jordan]

If you have a limited number of fish that are surviving in a 200 gal stock tank there should be absolutely no need to pre cycle a 1900 gal pond before adding those fish, that extra 1700 gallons gives you a huge safety buffer giving plenty of time for the pond to "cycle" itself before the fish could ever produce discernible ammonia levels in a pond that size.

?

 

[Mucky_Waters]

?

1900 - 200 = 1700

 

[Meyer Jordan]

Let’s do a little math.

@Alanw has 4 18’-20’ Koi and 4 6’ Koi.

Daily approximate Ammonia production is-

-assuming 2 18” and 2 20” fish =

18” = 320.5 mg x 2 = 641.0 mg/day

20” = 439.8 mg x 2 = 879.6 mg/day

6” = 11.85 mg x 4 = 47.4 mg/day

For a total of 1568.0 mg/Ammonia per day.

In a 1900 gallon pond this equates to 0.825 mg/g or 0.218 mg/l

This equates to an Ammonia level of 1.5 mg/l after only one week and will continue to climb albeit at a slower rate. A level of 1.5 mg/l can be an issue even at a water temperature of 50F.

Considering that the population of nitrifying bacteria takes almost a full day to double in size, using ‘seed’ water, though helpful does not grant Carte Blanche to return the full fish load to this pond. The bacteria population cannot be expected to keep up with the Ammonia production for the initial few days. Nitrifying bacteria when in the planktonic state are unable to oxidize either Ammonia or Nitrite. It is only when they are in the consortium of a biofilm can this process take place. Biofilm needs be reformed in this entire pond given a new liner has been installed. So there is no immediate Ammonia conversion taking place at any significant level.

@MitchM ’s suggestion of a ‘fishless’ cycle is the only logical, and safe, path to proceed assuming that the fish can be kept without issue in the separate holding tank. If not, the fish can be added one at a time over an extended period beginning with the smaller fish. Frequent monitoring of Ammonia levels must be observed.

 

[Tula]

@Meyer Jordan , are you saying a pond can not / should not, be cycled with fish in it? I never considered my koi as sacrificial fish when I put them in my new pond. Are you saying that we should not be returning our fish to the pond, if we had a new liner installed, until we cycle it with ammonia? Aren't the OP's fish in a stock tank now?

 

[TAHOE]

I've never "fishless cycled" a tank or pond. I don't do crazy water changes every week either and have never lost a fish during the cycle.
The OP must have a decent filter to be keeping these fish in only 200 gals, if he switches it over the pond along with the 200 gals of seed water, he already has a mature filter with bacteria to take over on the pond.

 

[MitchM]

As humans, we would have a lower quality of life if we were living with damaged lungs. It isn't simply a live or die condition.
Fish are no different. If their lungs have been burned by high ammonia levels (gill hyperplasia) they may still live, but their ability for gas exchange and waste disposal will be reduced, plus they will be more susceptible to bacterial infections. They will have a lower quality of life and a shortened life span as a result.
Fish should not be placed in an environment where their waste byproducts can accumulate to harmful levels.
Is it really that hard to be patient and make sure the pond or aquarium is safe before adding the fish?

 

[Meyer Jordan]

@Meyer Jordan , are you saying a pond can not / should not, be cycled with fish in it? I never considered my koi as sacrificial fish when I put them in my new pond. Are you saying that we should not be returning our fish to the pond, if we had a new liner installed, until we cycle it with ammonia? Aren't the OP's fish in a stock tank now?

No, that is not what I am saying. I believe that I stated that fish could be added to an un-cycled pond, but only gradually. Adding several fish, especially large fish, at one time is an invitation to disaster. As @MitchM pointed out, permanent gill damage can occur in a relatively short period of time, forever placing the fish in a condition of less than optimum health.
The use of products such as Prime will block such damage but since daily application is required for success, this could get expensive depending on the size pond and fish load and if you miss a daily application you will have an Ammonia spike that may prove to be even more harmful to the fish.

The real reason for my 'Math' example was to emphasis exactly how quickly Ammonia can reach toxic levels in an uncycled pond.

if he switches it over the pond along with the 200 gals of seed water, he already has a mature filter with bacteria to take over on the pond.

This is true and a workable solution but only if this filter is cycled.