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.
In 2005 I received eggs of A. elongatus “Ezeiza” incubated in Sphagnum magellanicum and eggs of A. vandenbergi “Talon Cansado” in the same material last year. I decided to give this spawning material some extra attention and offered it to fish as spawning material. For one of the samples collected like this and currently seven months old, I tried to determine the state the embryos were in. To my surprise, that was very easy! After some drying, eggs started rolling out of the moss. For example, the one on the photograph, which is A. cheradophilus “La Paloma”. Will definitely experiment with this spawning substrate further!
Some peats are just so packed with eggs you can’t miss them. This one we’re drying out a bit for an experiment at Foljuif. It’s has been filled with eggs by a group of Austrolebias gymnoventris “Castillos”. If you zoom in, you can see eggs that are still clear, in at least one other you can see the embryo’s eye. We take care that these don’t die while drying the peat.
Not easy to get decent pictures of detritus worms while they move around in my jar cultures. Here a collage of a rear end and a front end. The pictures were made with a dinolite USB microscope. All the small specks in the pictures are alive as well. Will need to use a different setup to photograph these, probably a water droplet, and a lot of patience.
For a few years now, I hatch my fry during winter in a small incubator with a Peltier element, kept at 22 degrees inside. It works really well, so that I even leave the fish in for a few weeks while they are fed with Daphnia and Artemia. So the fry swim in between other boxes and bags with eggs in a moderate amount of light. These boxes and bags around them are the really crucial ones at times. When I store peat on the shelves in the room or garden, hatching becomes less predictable than when I store the eggs in an incubator. So I try to behave in a safe manner now and store – per line – one box with lots of eggs in an incubator. I need to hatch it then after some four to five months. I tried to maintain lines just on the basis of boxes stored at less controlled temperatures, but that turns out to be tricky sometimes and with some risk if eggs need to be stored for long. Some additional certainty is comforting and the incubator as a back-up is taking little space. In there now, swimming happily: A. viarius (Valisas).
I’m experimenting with cultures that I can basically pour into the fish tank entirely, once “mature”. The culture I mean. For now I’m trying things in 0.5 glass jars at home on a shelve with moderate daylight. I’ve added tap water, a few Daphnia and small detritus worms that I scooped from a rainwater drum in my garden. On the bottom there are some specks of cocopeat and I fed the system a few times with dried yeast. So far, the Daphnia multiply, the worms too, the yeast seems to persist. Things go well. One jar had a solution with some drops of coffee creamer standing in it for a week before the water was replaced and the other animals were added. The cream had created a film on the glass in which the worms indulge. Next challenge: Massively increase the surface where the film can settle which hopefully increases the worm fraction. The nice thing about that is that I won’t pour the surface covered with film into the fish tanks with the feed. On the photo: few of the worms. If you magnify them a bit, you can see their chaetae.
Sometimes I have tubifex that can’t be fed to the fish immediately. I used to chuck it into a tank, where it would do well, but often it would be difficult to recover. Then suddenly I remembered a remark by Herman Meeus, how people used to “fish” tubifex by putting a burlap sack on top of the substrate. I applied the technique to my tank, and it works! Let’s see if this can be the start of a new food production method…
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.