My fishkeeping hobby used to be all about
killifish in aquariums. At an auction years ago, I bought some Aphanius mentho which had been bred outside in tubs over the summer. This got me interested and I began researching various forums (mainly Dutch and German) and finding out about people’s experiences of keeping temperate/ subtropical fish outdoors. I put together a wish list and was able to build up a small collection six years ago. I have kept breeding groups going of these ever since. They are mainly killis but also a few other types.
Here I am going to share a bit of that side of the hobby and write a little about the different fish I have kept this way, and my plans for keeping them in my new ponds. I know it is not everybody’s cup of tea but having experienced how little information there is out there, hopefully this might be of use to someone looking into this niche way of keeping fish.
I don't use any filtration in any of the tubs, I just pack them with lots of oxygenating plants. The tubs contain at least one basket of giant vallisneria and as well as free floating hornwort and Elodea. At water level (on bricks or on a submerged crate), I have baskets of reeds or bulrushes, the roots of which provide more cover and some water mint and other marginals which float across the surface. I keep the water 10cm from the rim of the tub. Once a year, in preparation for winter, I clean out the tubs, mainly to get rid of the debris built up on the bottom. It is also an opportunity to examine all the fish before the winter.
The location of the tubs is important and ideally they should not be in the sun all day. As they contain only small bodies of water, temperatures would rise too much. Digging them into the ground would be best although I have managed to keep them above ground grouped together, with some shading others and marginal plants also helping provide some cover. It also depends on the fish. Some of my fish naturally occur in shallow pools which heat in the sun while others of mine come from rivers which stay cooler.
From mid-October/early November, I group all my tubs together and cover them with a couple of layers of plastic. The plastic provides insulation but also has the benefit of protecting from falling leaves and against excess rain water which could make the water too acidic. At this point, I have removed the marginal plants and only the oxygenating plants remain. The tubs then stay untouched until March next year. I would add a note of caution to this approach as the winters over the last few years have been mild. Digging them in would offer more protection.
Keeping fish this way requires a lot less effort than in aquariums. Many subtropical fish actually benefit from being kept outdoors for at least part of the year. Of course different subtropical fish have different temperature tolerances and only a very few available ‘aquarium fish’ can be kept outdoors all year round. The seasonal temperature changes, including winter rest, are good for them, as are changes between day and night. Exposure to sunlight is another benefit. Their diet will be much more varied (insect larvae and critters among the debris) and they do not need much additional feeding. No filters to clean, just topping up the water every now when the weather is really hot. Half the year, they hibernate and need even less care. To raise fry, I set up smaller tubs packed with plants and place any baby fish I come across in there, for them to grow on over the summer without any further input needed. Collecting fry needs to be done before the winter clean-out as it will otherwise not be easy to find them among the mud when emptying the tubs.
MACROPODUS OCELLATUS
Into my middle pond, I have introduced this paradise fish seldom seen in the hobby. The location is from the Yangze river in China and this strain is fully hardy.
I had two 250L tubs with about 20 of them in each. In addition, for breeding, I had a group of about 15 in a large but shallow tub (approx 40cm high and a diameter of around 1m) which heats up fast in the sun and this seems to be beneficial for breeding, although I have bred them in larger and deeper tanks in the past also. These fish do not live long, about four years, so it is important they breed while they are two and three years old. I place about five males in the breeding tub with a higher number of females.
The male builds a nest underneath a floating plant leaf or algae pad. You can sometimes spot the bubble nests when lifting a lily pad. In September, I scoop out the young fish as much as I can. With lots of plants in the tubs I could still collect enough fry each year at the end of the season. The adults I leave outside but the young fish go inside for the first winter. In previous years, I raised loads of young by setting up another tub just for them and regularly scooping baby fry from the breeding tub throughout early summer and let them grow up for the rest of the summer in this dedicated tub. This nursery tub will be full of fish by the end of the summer using this method. Baby fish can be scooped from June onwards or even May if we have hot spring weather.
Over the last few years, I raised enough of the M. occelatus to stock my middle pond with about 30-40 of them.
WHITE CLOUD MINNOW
For the last three years, I have kept four white cloud minnows in a small preformed pond in my garden. I never found any fry, perhaps because this pond is always full of dragonfly /damsel larvae and baby newts. The fish originate from my uncle’s pond in the east of Holland, where winter temperatures are a lot colder than here. He has kept them like this for over 5 years.
The WCMs have joined the occelatus in the middle pond.
APHANIUS MENTHO
This feisty little killifish comes from the Turkey/Iran region. I do not know the exact location of mine. A. mentho has a reputation for being aggressive. In the past, I was able to sell excess stock of my other outdoor fish to a LFS which has reasonable collection of temperate fish but they would not take the menthos as they had previously experienced males wiping out each other. Strangely, I have never experienced any trouble in the 90L tubs I keep them in, or at least, they multiplied in large numbers overall. For a few years, my mentho tubs became over-crowded as a result. In the end, the tubs became overgrown by the reeds and available space reduced and the population became smaller accordingly. The fact that the tubs were packed with plants and roots from the reeds might have helped so many males to co-exist. Or maybe the sheer number of males in one small space made them give up on keeping a territory. Anyway, I found this to be a really easy fish to keep outdoors. In the early years, I used to collect their tiny eggs from the algae pads but I stopped doing this when I realised this was not necessary. The menthos have gone into the second pond from the house.
FUNDULUS JULISIA
Last month, I cleaned out three 250L tubs containing Fundulus julisia. Known as Barrens Topminnow, this handsome killi occurs in only a handful of locations in Tennessee USA and is on the Red List of endangered species. I keep groups of about 15 in large tubs of 250L all year round. Out of the fish I keep in tubs, these are the least shy, though they still make a dive for it when I approach.
They breed over quite a long season, from about May onwards. They like to lay their eggs in filamentous algae. The picture of the egg was taken in late September, which goes to prove they lay at least until start of autumn. To collect baby fish, I scoop a jug or bucket into the floating plants from time to time and locate any I catch into a separate smaller tub I set up just for them. The nursery tub is full of plants and I leave them to their own devices until October, when I take the youngsters inside for their first winter. When I was trying to raise fry in greater numbers, I would regularly clean out the algae pads from the big tubs and place the eggs in another tub or just chuck the algae pads into a bucket with water and remove the fry from there. This year I did not scoop out fry as the months went on. I only started looking for fry over the last couple of weeks and only collected 7 young fish which is a shame.
I placed about 30 adult fish in the large pond near the house and hopefully will reproduce there. I held back 15 and kept them in a tub to breed further next year. Compared to other fish which I have recently released into my new ponds, I see F. julisia most often.
It seems a bit strange that a fish which is so easy to keep and breed is on the brink of extinction, although huge efforts are underway to save the species. Out of the killis I still maintain, F. Julisia is my favourite which is why I decided they can have the large pond near the patio.
FUNDULUS CATANATUS
The Northern Studfish from southcentral United States can grow up to 15cm. I think might be the largest killifish there is and males are stunning in the summer months. I was able to buy five young fish back in 2016 but they have not grown larger that 10cm in my tubs. Breeding them involves a bit more effort. In the wild, they lay their eggs in the gravel of river beds and I did not see any young appear I the first few years in the tubs. Last year, I tried placing a pair in an aquarium with flowing water and gravel on the bottom. Unfortunately, the tank sprung a leak and I had to put the fish back in the tub outside. A few weeks later, I noticed eggs in the gravel of the tank. They had fungus on them but at least I knew the system worked. This year, I placed a tray with gravel near the water surface inside the tub with a pump providing some directional flow. I scooped six small fish over the course of the summer and am raising them indoors.
It is a shame it has taken so long to work out a way to breed them as given their size, it would have been great to be able to release these into the ponds also. I am keeping the adults in a tub however, in the hope they might breed again for one more season, despite their age and the fact I only have one remaining female.
Since becoming so busy in the garden, I know I won't have the time to keep the tubbing project going and with the ponds this side of the hobby must culminate. Just because the fish did well in tubs however, does not mean they will thrive in a pond.
First of all, pond water is more likely to become increasingly soft due to the heavy rain in the winter months (in contrast, the tubs are covered for six months of the year). This could become an issue for the Aphanius and Fundulus species which prefer harder water. I need to learn a bit more about ways to maintain a certain level of hardness in the pond – any advice would be much appreciated.
Secondly, the Aphanius and Macropudus live naturally in shallower pools of water which heat up considerably in the summer sun. This may not happen in a pond as much as in a tub and might also affect their breeding potential.
Finally, I am afraid the biggest risk is going to come from herons, which may well put an end to my journey of keeping of at least some of these fish. I have seen them fly over occasionally so visits will be inevitable. One of the reasons for holding back some of the breeding stock in tubs is so that I can still pass on these rare fish if I cannot maintain them in the ponds. For the large pond right at the back, where herons I assume will be most comfortable, I am thinking of introducing minnows next year, which would hopefully multiply and cope with the visits. I am not going to mess around with nets or plastic lines etc and would rather put up with the consequences of heron visits. If that means I will only end up with sticklebacks and minnows, so be it. But after keeping them going all these years, it would be nice if at least some of my populations could sustain themselves in their new homes.
Pond number four (second from the back) I am hoping to keep fish free, as a wildlife pond.
