New fish disappearing

[Rayers]

Hello,
I am new to this forum and am really glad I have found it. I've been 'ponding' for about 30 years, but only recently have I taken up the maintenance of our garden pond, so am more interested in looking stuff up on the net. I'm based in Switzerland.

My first question is about where my new fish go to. Since 2020, I have regularly introduced about 10 newbies to our pond between April and September. The smallest in the shops, around 4-5cm. Our pond is roughly about 7000lts, 1m deep max, several levels, with quite a vigorous waterfall. It has a strong pump system and a skimmer. It has five max 20cm Orf and one young Koi (around 15cm) and about 15 regular goldfish. I respect the time suggested by the shop when putting the fish into the new environment, which is basically to keep the fish in their plastic bag - opened - in the pond water for between 15-45 minutes depending on the difference in temperature, then gently allow out.

This pond and its population does not generate new fish. Our previous ponds did. Probably something to do with having Orf and Koi now? So I buy in. We redid this pond in 2020 so the population is relatively new. I've had a couple of heron episodes which also have made me buy in newbies. The heron episodes could be a whole chapter (!).

I question what happens to the new fish. If I put in, say, around 10, I can kind of garantee that over half will just disappear immediately. Is it the pump? the skimmer? I check the skimmer regularly. No fish in the skimmer. Are the Orf eating them? I look at my Orf and I don't think they are big enough to eat 4-5cm babies, but maybe they are? Do these little ones go into the overflow? I'm curious. Should I invest more money and buy larger fish? I don't generally, because of not wanting to finance the local heron's diet. I have never actually found a fish in our pump filter system, but I am also aware that I cannot see into the 8 sponge filters, I only can easily check what come onto the moving mat area above the filters, which is usually green algae looking stuff. Last weekend I cleaned all the pump filter system and although it was really dirty (so satisfying to clean!), no colourful bits of baby fish to be found there. Tadpoles from time to time, but no fish.

I have, this spring, spent quite a considerable time and money on repotting / adding plants and adding extra hiding places for the fish, to help against predators, so I am aware that these little ones could just be hidden somewhere. But this is such a regular thing I thought I would ask anyway. Your thoughts and experiences?

 

[hamstermann]

Welcome to the forum! Unfortunately I don't have any experience that qualifies me to give advice. I do have some questions and suggestions though.

Are snakes or other fish-eating wildlife a possibility? Could you put a motion-detecting camera on your pond so you could see who/what could be fishing in your pond?

 

[Rayers]

Hello Hamstermann, thanks for answering. My 'Heron' experience means that I have become a bit like the Crazy Neighbourhood Lady whose sole aim in life is beating away the dreaded bird. I do luckily have other people in my life to center me a little, but I have, so far this season, once again fitted in movement detectors that flash and use a high frequency to discourage the birds, plus stringing up loads of lines of fishing thread above the pond area (higher than human height) that flash in the sun, plus adding in these hiding areas. AND covering over the shallow areas with hexagonal meshing that floats so I can offer protection from the bird that way, too. As I said, it's a whole chapter in itself. Our pond doesn't really allow for a full net covering so I have to adapt stuff. This March, four of my five beautiful butterfly koi were taken. I was so frustrated. Hence the minor battle since then.
Apart from herons, I imagine that hawks might be an issue. No otters or snakes here. And I imagine that the larger fish would be targetted more than the new babes that disappear within hours.

 

[Lisak1]

Welcome to the GPF!

I've had new small fish disappear, too. I think they just die and the bodies are never found. No matter how careful you are in introducing new fish, sometimes they just don't transition well. I have a rocked in pond, so they could be getting lost in small spaces between the rocks either before or after they die. I really doubt it's the other fish eating them , but we do get some large bullfrogs that will eat anything that fits in their mouth, so I do suspect it's one of them from time to time.

In addition to our big pond we have a small patio pond. I've taken to using that as my "nursery" for the newbies and letting them get some size and making sure they are healthy before putting them in the big pond. It's fun to get to know they up close before I turn them loose!

We'd love to see pictures of your pond!

 

[Rayers]

Thanks, Lisak1. Feeling reassured that I'm not the only one. I'd like to know more about the 'nursery'. Do you have a pump in it? I was thinking that I could potentially have a kind of nursery space, yes, to a) get to know these little ones better before putting them in the big space, but also to protect them - and the pond fish - from I guess viruses and such. Could you tell me more about yours? I have uploaded a couple of just now photos of the pond. You can see the hexagonal plastic floating protection I have put around the edges in the shallower areas, protection against herons and cats.

 

[j.w]

@Rayers

I love your beautiful pond and fish!

 

[Rayers]

Thank you