Inside the wooden house, there is still fry approaching maturity. They were born a few weeks ago and have been fed once with Artemia, after that with pond invertebrates. Now they will need to overwinter at relatively small sizes and without heating. Critical to make this work seems to be using tanks with a large surface and low depth and to have sufficient thermal mass in the house. When I see a plastic box in a shop, I get the feeling I can predict how many I can raise in there to maturity, just by looking at the surface area. Maybe it’s time now to start experiments on density-dependent growth and survival in my fish.
In the house I also store orchids (Zygopetalum), palm trees (Archontophoenix) and citrus (Yuzu, finger lime) during winter and cuttings of Physalis Peruvian groundcherry.
To keep tanks clean(er), I decided to use plants that grow well and root well in water as filters. Here on the photograph three different plants on small floating islands in my fish basins, situated in an unheated greenhouse. They all grow through winter. Leftmost: Vietnamese coriander (Persicaria odorata), middle: Japanese parsley (Oenanthe javanica), right: watercress (Nasturtium officinale). What’s really great is that the plants need to be kept growing to make them take up nutrients. What helps well for that is harvesting them, and all three are edible. Aquaponics in its simplest form.
The coldest days seem to be over now. This picture is from last week. In my barn, most tanks still hold fish. This man is over a year old now, it’s an elongatus “Gral Conesa”. It is overwintering in an unheated garden shed, that does catch some sun during the day. So far, so good.
For a while I try to raise small fish without much Artemia. It decays when not eaten, it can feed predators of the fry. I’m down to two to three feedings of Artemia now, without much mortality. From day one, I add a mix of living invertebrates to the tanks, as in the video. Chaoborus larvae are removed from the mix, large Culex as well. The tank gets some tap water so that the water does not remain too soft and abundant java moss. Per day, some extra (rain) water is added and food if necessary. For this extensive setup, population density is critical: the tank surface per individual should be some 100 square centimeter. So for really large groups, I need to switch back to an intensive setup with water changes etcetera.
Always funny to see what starts growing in small trickle filters after a while. This one – an Adiantum venustum I presume – managed to grow through a small hole in the lid of the container. Must like the peat accumulating inside.
It’s done. In France, 31 tanks with Austrolebias are now outdoors in a shaded tunnel.
All fish were transferred in water of which about 50% is from their original tanks, and the rest aged tap water.
Tanks are in different sizes, and numbers of fish per tanks are so that it is easy to feed them: the amount to be fed is proportional to tank size.
13 Tanks have a breeding container now. More will follow. The species are A. elongatus (General Conesa, Vivorata, Ezeiza, Villa Soriano), prognathus (Salamanca), vazferreirai (Parque Rivera, Arroyo de las Viboras), viarius (Valisas), paucisquama (Sao Sepe), bellotti (Maschwitz, Villa Soriano), nigripinnis (San Juan Missiones, Maschwitz), melanoorus (R5KM399), robustus, charrua (Canal Andreoni, Ruta1316).
Last week, there have been two nights where air temperatures have dropped below zero. Most fish were moved to their winter quarters just before that. They will stay in a frost-free greenhouse until April.
Alltogether, there are some forty basins with fish in the greenhouse. In there, A. elongatus, prognathus, cheradophilus, viarius, charrua, bellotti, nigripinnis, vazferreirai, arachan, gymnoventris. The tanks are filled with tap water and contain a tiny amount of peat, some dead leaves and a starter of tubifex. Food will be supplied on a weekly basis and adults get a spawning container. They will continue to spawn through winter, on an irregular basis and depending on temperature variation.
The weekend promises to become very hot, in the Netherlands it might reach temperatures unseen after 1994. I try to reduce warming up of the fish tanks in my wooden fish house as follows. All tanks, even those without fish, are filled up with fresh water as much as possible. A ventilator powered by a solar panel assures air flow throughout the day. All windows are screened, so that no tank receives direct sunlight. Tanks are covered with plastic panels, such that evaporating water drips into the tanks again.
In France, the fish are now in plastic tanks in this nice tunnel with shade cloth. Rain drips through, so far it does not get too hot inside. The tanks contain nigripinnis, bellotti, vazferreirai, prognathus, elongatus, wolterstorffi, charrua, gymnoventris, cheradophilus. The adults are laying eggs very well.
The last few weeks I hatched fry from several species. In some cases, there are lots. Due to space limitations, I decided to put a few groups outdoors. Before that, they were fed twice with Artemia. Then they were put in 70 liter tanks with a stock of invertebrates that I fished and sieved from a ditch. Things seems to go great! There are some casualties of course, as the photo shows, but overall everything goes well and the fry even seem to grow faster than ever. The fry are from Austrolebias prognathus “Salamanca”, and charrua “Ruta1316”. If all goes well, I might do this more systematically.