Having removed fish to a holding tank, I drained my pond (4,500ltrs) and cleaned out most of the sludge and weed leaving a small amount to maintain eco system. Refilled, dechlorinated and fitted pressure filter with foam, biological filter and UV. Reintroduced fish to pond. Out of 20+ fish 13 survived the move. However, they now stay together at the bottom of the pond and even when swimming around they do so in a shoal. They also do not appear to eat floating pellets as before. The move was 14 days ago and I guess they are traumatised. How long do they take to get over it and is there anything action I can take.

They aren't traumatized, they're terrified. Without cover, they just know anyone coming to the surface or breaking formation is going to be eaten by a passing heron (or hawk or cat or snake...). Give them something so they can't see the sky - an umbrella, a pond lily...

You can't replace that much water and add a filter on top of it without losing fish - there just isn't enough bacteria left to do the job and there was also a major water chemistry change they had to deal with. I'm surprised you didn't lose all of them.

Pond is planted with lily and there are several areas in shade with over hanging trees. 6 fish died in the holding pond filled with original pond water. Lack of air I think. So question is how long do you think they will stay "terrified" .

You need some "dither" fish. Koi move around a lot and that can bring out the shy fish.

Good luck. I know it's horrible losing fish.

Mindi

I'm surprised they aren't coming up under the lily pads. Maybe you do need some Dither Fish. Your pond is big enough for koi.

Have you tested the water for ammonia and nitrites?

And chloramine?? It won't be removed with plain dechlorinators and is toxic to fish.

Thanks to all for advice. Trying the dither fish.

The bigger problem may still be water chemistry. That's something you can't fix, it will just take time.

You can take a sample of your water to a pet store and they can test it for you. Also there are water testing kits there as well. Still think the either fish will help the other fish to become less shy.

Mindi

Never having heard the term 'dither fish' I just researched it a bit and learned something new. For other non-fishy people, a dither fish is one which will not be a threat to the other fish but will reassure them that all is well in the water world. Typically, they will be top swimmers so the fish in hiding will see them free swimming and not getting murdered. Or whatever it is fish might think.

I'd never heard of that term either and I've had pond fish and aquarium fish most of my life.

You might have more advice than you want, but...My guess is that the cleaning upset the balance of nitrifying bacteria, producing an ammonia spike, the new water was much different than the old water (pH, hardness, temp), or the cleaning allowed pathogens to become established. Goldfish like hard, slightly alkyline water. I doubt the fish are traumatized. I think it's the water parameters.

How are your fish doing??

😀

Mindi

I sought advice re "dither fish" from local aquarium and pond retailer. Bought some fish and put them in with the others. Didn't see them again for 3 days, then they appeared in the shoal of goldfish which still lay huddled together at the bottom of the pond. They seem to have joined the group doing nothing but keep to the bottom and very still. Interestingly they all face the same direction. Went back to retailer with water sample which turned out to be very high in nitrates. Bought some additive balls which gradually turn into a gel to put into the pressure filter. Retailer says it may take some time for the water to stabilise ( 2 - weeks) We shall see !!

The best way to remove nitrates is to change the water...unless you have nitrates in your water supply.

Need the good bacteria to build up and then remove the nitrates after stabilization. I think that is why he gave you the balls. You can buy bacterial supplements, but might not be economical in a big pond. I would leave the survivors alone at this point since they are surviving. Goldfish are very dirty fish as Iam sure you know.

Good luck!!

Best wishes for your fish!!

😀

Mindi

Hi Nuttalli, As you can see from previous posts, my problems started when I did change the water. However, the fish seem to be a lot calmer now and swimming about feeding as they should. Now another problem. I have an auto cleaning pressure filter with UV. When auto cleaning I collected the waste water in a large tub. There now appears to be a lot of goldfish fry in the tub !! How they survived the filter who knows. Anyway I don't mind a few more fish as the pond is big enough but out of the pond what to feed the m on? Any ideas.

Oh no!! How big are the fry??? They probably had plenty to eat before the pond was cleaned. In such a big body of water I don't know what to tell you. Not sure how you would target feed them. How big is the tub? Maybe they are finding food in the waste water and that is why they are alive. It depends on how big they are.

Little troopers making it through the scary filter. 😀

Mindi

They are quite tiny, dare I say similar to sperm and quite active. Pretty sure they're not tadpoles.