Number of Fish in a Pond

no1catman

I remember I had a builder come around for some problem, he also had a pond, he was amazed to see three-year-old fish in the process of changing colour - two-tone red & dark brown! He confessed that, he would take his 'dark' ones out and dump them in the moat of Caerphilly Castle!

Froglet

Some never change colour,I have fully grown fish like that but would never dump them somewhere else.I have rescued many unwanted goldfish in the past but would not do so now,the last 2 resulted in all sorts of problems with my resident fish and so never again.Besides I have too many now !

teddysmum

I thought I read, some time ago, that fish adjust the population to fit the surroundings, provided that you don't interfere by adding stock.


I have a 3ft tank with platies and they seem to do this, keeping numbers fairly constant. When two or three oldies die off (they seem to go in groups, probably as they are the same age/of the same parent) a batch of young appear, but only a few mature.

Froglet

In a pond environment,and especially in large,well planted ponds like mine,there are plenty of places for fry to hide,and so I don't think the males chasing the females to get them to spawn stop and think,oh hang on there seem to be a lot of fish in here already! I only wish they did.I wish they would invent the pill as well.


Whereas in a tank there are very limited hiding places,and as live bearing fish keep producing young,there is a lot of inbreeding which weakens them further.

Froglet

JP08 wrote: »

Agreed, it seems very sad.

Spotting the young/eggs in the pond is practically impossible - I didn't even notice these until some of them had got to 5cm or so in length. One is even big enough to start changing colour.

From [some of] the calculators for fish length etc on line and the size of that little Hozelock pump/filter/UV beastie (which is rated for best part of three times the size of pond it is dealing with) I may have a couple of years grace - provided that there's now enough fish in there to eat all of next years offspring.

Will see how things go. Maybe I'll just feed them less.

Fry seem to stay in the one place for a couple of weeks,near to where they were hatched so if you spot them spawning,either remove the weed with eggs ,and let it dry out,or ,once born,plunge a bucket into the area you think they are.


You could feed a little less a couple of weeks after spawning,but bear in mind that fish need building up for the long winter months when they don't get fed,and once the cooler weather comes,before the start of winter,wheatgerm pellets do not give them those nutrients in the same way.

Fosterdog

teddysmum wrote: »

I thought I read, some time ago, that fish adjust the population to fit the surroundings, provided that you don't interfere by adding stock.


I have a 3ft tank with platies and they seem to do this, keeping numbers fairly constant. When two or three oldies die off (they seem to go in groups, probably as they are the same age/of the same parent) a batch of young appear, but only a few mature.

It does depend on the conditions in the tank, I had one tank with platies and only had a few plastic plants and there were never too many fry. when I redid the tank and added real plants and quite a lot of them the population exploded and it wasn't long until the tank was getting overcrowded. I ended up swapping loads of my young but decently sized platy fry for two dwarf gourami who helped control the population by actively hunting the platy fry but some still survived to keep my platy population at a good level with any extras being given to my LFS where I'd build up credit to use towards food and equipment.

no1catman

Froglet wrote: »

Some never change colour,I have fully grown fish like that but would never dump them somewhere else.

Define 'fully grown' - I had fish three-to-four inches long that started changing colour from dark brown - to multi-coloured. Many did after weeks or months, others could take years!

Fosterdog

Colour can be determined by genetics, temperature, diet, water quality, predation levels, sunlight exposure (difference between a 1000l narrow but deep pond and a 1000l wide but shallow pond or an exposed vs shaded pond)

JP08

Well, nearly reduced the number of fish by one over the weekend.

Hoiked the plants out for a bit of maintenance as we do every couple of years - trim tops and roots back just because the pond is small and easily swamped in plant life. It also makes getting the netting frame off easier and gives me an opportunity to remove the timber cladding from the pond to inspect the steelwork holding the tank in shape (nothing complicated, a couple of box sections of steel along the long sides and two threaded bars across the end).

Anyhow, the plants were out for a good hour or so sitting on the lawn. On their replacement we found our suicidal adolescent fish (the largest of the baby ones - reckon it's last years at least - came home the other week to find it on top of one of the lily pads) on the lawn under one of them. As per the previous occasion, picked up and popped back into the water and off it swims ...

teddysmum

I seem to recall reading (quite a long time ago) that fish like goldfish slf regulate to fit their surroundings.


This seemed to be the case as I had an aquarium with 6 smallish goldfish, which were not replaced if one died and the ones left seemed to grow much faster when one died off. I was eventually left with one very large fish, who went to a good home in a pond, with lots of companions.


I have platies in my current tank and far more than recommended, but they seem happy, as they breed, with this breeding increasing when a few die (Rarely singles; I believe because they will be of the same 'hatching'/ life expectancy).