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.
May and June are for hatching alevins and raising them. I’ve noticed that I keep on getting the same numbers of juveniles for each tank size or type. There are some species effects of course but things are rather predictable, as if their populations are regulated. So I can more or less calculate how much fish I can breed like this per year. The alevins are hatched with rain water after storage at home for at least five months. Then they are fed Artemia once, and a mix of zooplankton after that. I tend to keep them inside for the first two weeks, but I’m thinking of changing that, because I have bigger tanks outside. This is of course not what you should do when you have for example only two alevins of a precious species to save your population. Then put them next to your bed.
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.
Juveniles are piling up. I initially keep them per one to four in small one liter containers, until they are about 1 cm. Then they are transferred to shallow 10 liter trays or larger tanks. Much of what I raise at the moment is on this shelve, some 20 containers. All containers are checked daily, the fish fed, etc. Mortality is very low like this. The room has only mild heating, but I do make sure it’s warm enough for at least a few hours so the fry eat daily. The temperature does not drop below about 14 degrees. The most difficult and precious fry are not here but kept inside a small incubator for their first weeks.
October. It’s getting chillier at night. I have stopped hatching in the wooden garden house. The fry that hatched in September, is still being fed with small zooplankton and some Artemia added once or twice a week. That goes fine so far. Growth rates seem OK, so that I expect them to sex out in a few weeks. Meanwhile, I am checking all my boxes with peat, to find out which ones have many eggs and which ones few. Autumn and winter are good periods to plan the coming year…
Sometimes the weather is just not doing what you need. Recently hatched fry seem most sensitive to this, according to my impression. Some species seem to suffer more from cold nights than others. I’m using a small and relatively cheap Peltier incubator (Herp Nursery II) to keep some fry at relatively constant temperatures. What I do at the moment is raise the temperature to 25 degrees (C) during the day, and lower it to 20 when I go to bed. It seems to work well! Alevins of Austrolebias patriciae “Fontana”, aff. patriciae and paucisquama “Sao Sepe” all eat, grow and survive very well.