Wednesday, 21 June 2017

Breeding goldfish in your garden pond

There is a huge amount of complicated 'advice' about breeding goldfish - especially food for the very young fish (aka fry).

The truth is, unless you want to breed as a business, it's really easy:

Your top priority is to keep your main pond (#1) healthy. The commonest problem with newcomers to fish keeping is over feeding. An established pond (12 months +) will produce more food than your fish need, most of the year.

Nutrients are continually finding their way into the pond through visiting birds and insects (the latter being caught and eaten!), so the "closed ecosystem" of the garden pond more often needs help to reduce its fertility (see 'filter' below).

You need a bird and cat proof cover (e.g. netting) to protect the fish; also a pump and filter. A good filter contains porous stone which has a large surface area on which beneficial bacteria thrive. These convert toxic ammonia (from  fish droppings) in to toxic nitrite, then into non-toxic nitrate (which is fertiliser).

The nitrate causes plants and algae to grow more quickly, and a pad of microfilter can be added to your pond filter to remove algae and other fine particles. When you first start using microfilter the gunk it collects will likely be brown. This is dead algae (for example) and fish do better without living in this 24 hours a day. It took a few months to clear this when I first added microfilter to my pond filter.

Using ultra violet light to kill algae makes dead algae! Dumping this on the bottom of your pond makes little sense. Better to have live algae and manage it ... the reason being:

Green water is healthy, in moderation, and the food of choice for all the microscopic plants , animals, algae that thrive in a healthy pond.

It is the best food for daphnia (aka water fleas, but they aren't fleas!), and daphnia are the best animal protein for baby goldfish as soon as they can yawn wide enough ...

female daphnia with eggsIt pays to breed daphnia in a small separate pond (#2) because healthy goldfish will find every edible daphnia in your garden pond (#1) in no time. A 3rd small pond is ideal for the baby goldfish.

N.B. Extra ponds, if made of containers, need to be buried in the garden to ensure a good thermal contact with the soil. This helps to stabilise the water temperature. A tank of water in full sun will experience suhc rapid fluctuations of temperature on a summer's day that fish, and even the plants will die.

It is fun hatch baby goldfish indoors in an aquarium, but if the weather is okay, (pond temperature > 10 C) they do better in pond #3.

Goldfish spawn onto plants. If you are short of pondweed, then place willow twigs in pond #1, ans after the fish have spawned, move the twigs to pond #3.

The best food, for newly hatched fry is green pond water! You can't buy this at a pricey garden centre, but ti is free from you pond!

The best food for daphnia (which are the best food supplement for goldfish) is green pond water!

When fry reach about 1.5 cm they can't eat 'adult' daphnia, but they can manage their tiny offspring.

As your fry / bambinos grow, add more daphnia.

If you smaller ponds don't have a pump and filter (mine don't) add fresh pond water regularly to dilute the fishes effluent. You can use such water on your veg and flowers and mine seem to appreciate it!

N.B. Test for NO2 regularly to check your water-replacement is adequate.

No matter how successful the breeding in ponds proves, it is interesting to grow some indoors in an aquarium - handy for you magnifying glass, camera ,etc ... especially if you suffer from mad professor syndrome :)

P.S. Once you know what a filter involves, you can make your own. If there is space for a large gravity fed filter, banks of gravel can be used to grow plants, using the fertility from the pond water.

 I also have a grass carp which sadly does not breed readily in a pond.

 Related: ecology, fish, gardens, hobbies, nature, self-sufficiency, carp


  1. I gave up on having fish in my pond due to the extreme winters we can have. It's expensive to keep a pond heater running constantly. My pond is deep but there still must be an air hole and the heater has to struggle keeping up against -20F temps. Now I have an aquarium with a few tropical fish and I enjoy them. Now that I know what it takes to have a successful aquarium it's no wonder my fish constantly died when I had an aquarium as a child. I didn't have a clue. :) As for my pond... it is mostly a bog with a waterfall. The frogs and toads love it. During the Spring mating season the sound they put out at night can deafen you! No sleeping with the window open! :D

  2. Some of the baby goldfish are in an aquarium, in case there are problems in the ponds. It amazes me how quickly they have grown. I'll add some photos to this post when I get a round tuit ...

  3. pH buffering garden ponds to protect fish during heatwave!

    Our recent heatwave (up to 34C) has been problematic for my pond. All the usual water quality tests are excellent, but being mainly rainwater, there are very little dissolved salts.

    The recent heatwave created a burst of vegetative growth which used up the nitrate (nitrate plus water = nitrous ACID) and CO2 (CO2 plus water = carbonic ACID). The result was a very alkaline pH which is not healthy for the fish.

    Fortunately, the solution is simple - add gypsum, which buffers the pH. I tried this last night, the alkalinity has decreased by 90% overnight and is just within the acceptable range.

  4. Treating rainwater for increased buffering in garden ponds.

    rainwater is too soft for a garden pond. The lack of dissolved salts reduces its pH (acid and alkali) buffering. Easy solution - add oyster shell grit, or similar, to your rainwater butts :)

  5. Lord Douchebag25 June 2017 at 19:29

    I was traveling down Woodfield road in a small village toward my storage area for spent fuel rods from U.S. nuclear plants when I stopped to view a pond someone had set up with goldfish. Since I hate nature and all to do with it I went about my way.

  6. Good riddance, your Lardship! Even the goldfish look pleased that you have left!

    How are your billions in the Cayman Islands?


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