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.
A small A. prognathus (Salamanca), some ten days old. I have been worrying about controlling nitrate and levels of other waste products in my tanks, to maximize juvenile growth of small ambitious fish like this. In some places the tap water is really excellent, in others it’s barely acceptable which makes the level of difficulty to maintain some species very variable. I also start believing that local tap water properties really determine how many people engage in the aquarium hobby and also determine the fish species that do well and are maintained in the killifish community. Wouldn’t it be nice if we could make some things “easy” anywhere?
In many situations, replacing water when it’s almost too late can help of course, but I prefer to be ahead of things, to avoid excessive levels to build up or to “clean” the tap water. So I am moving away from tanks with just some peat on the bottom, and I add zeolite now, just a little, to see how it behaves, what the effects are and if it might help to make raising fish easier everywhere. Plans are to measure lots of tanks and different waste product treatments later, in a situation where I start from dechlorinated tap water. Will be some work: all samples will have to be filtered and frozen before they can all be analysed together.
This afternoon I made pictures of one male and three females of Austrolebias charrua (Los Naranjales). They’ve been outside for almost three months now, and I’m happy to see they do well. Charrua is a real beauty and always a pleasure to find in your net in the field. There is quite a bit of colour variation, even between different generations of the same line. The flanks can be gold or grey, it is unclear to me what would cause that. Females can vary quite a bit in colour pattern, even on the fins. It often happens that I mistake a female for a young male.
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).