WildNothos
THE NOTHOBRANCHIUS SITE
Diet & Feeding habits of Nothobranchius Fishes
Nothobranchius species are generally micropedators, feeding on a range of small aquatic crustaceans, worms, insect larvae and other zooplankton. Live food is particularly important for these fishes due to their high energy consumption during the fast growth period as well as the high reproductive effort during the entire adult phase.
One species, N. ocellatus has evolved as a large predator and it can always be found together with at least one or several other Nothobranchius species. In particular, it is without exception found syntopically with N. melanospilus. Furthermore, the members of the N. microlepis species group have specially adapted gill rakers that allow them to feed predominantly on small planktonic crustaceans. The author has also on several occasions observed them, under captive conditions, preying on other fish, such as the smaller members in the same aquarium.
Feeding in Captivity
I try to feed my fish exclusively with live food, which contains daily portions of Artemia nauplii and Grindal worms. I often supplement the diet with food that I collect from nearby outdoor pools, such as planktonic crustaceans and different mosquito larvae. I also keep a large plastic container in my garden, where I regularly enter a portion of the small invertebrates collected from the pond. From that container in the garden I then take every other day or so a smaller amounts of planktons, in order to provide a more varied diet for the fish. I always have a small stock of frozen red mosquito larvae in the freezer, which I only feed in exceptional cases, if I would have no access to sufficient amount and variety of live food, but this is relatively rare.
Grindal
Grindal worms, Enchytraeus buchholzi Vejdovský, 1879, are amongst the most important cultivated live food for aquarium fish. The worms grow to about five to ten millimetres and thus ideal for both smaller size fish and larger fry. Its common name refers to Ms Morton Grindal of Sweden, who has been very active in the methods of culturing white worms, and who probably did not anticipate how famous her name would be among aquarists around the world when she had succeeded in extracting and isolating these smaller size species from other white worm cultures.
There are several different methods for successfully culturing Grindal worms. I culture them exclusively on coconut fibre. Below account represents my own way, which is running for me over many years now.
For setting up a culture, I take a plastic box and fill it for about 3 cm with damp coconut fibre. I soak a chunk of coconut fibre in water for a few minutes to allow it to expand. The substrate in the box should be damp to the touch but not soaking wet. I take some worms from another running culture and place them on the fresh substrate. I then add food to the culture, for which I use exclusively branded flake food. By consuming the flake food, I believe that the worms get gut loaded and they transport to the fishes the different vitamins and other elements present in the flake food. For the start, I just give a few pieces of flakes to the culture.
I lay a piece of cover glass on the top of the substrate and close the culture with a lid. As Grindal worms like warm temperatures, I place the culture on the highest rank of the fish room. For about two to three weeks, nothing much happens. During this period, I check the culture a couple of times. It can happen that the flake food slowly disappears during the course of a week or so, and then I provide a few more flakes. During this initial period, the worms are not visible in significant numbers. After a couple of weeks, the culture suddenly starts booming and the worms reproduce quickly. The flake food will then consumed by the worms every day and will provide the possibility to feed to the fish as a daily routine.
When the culture is running, I open the plastic box once a day. I lift up the cover glass, on which the worms are gathered. This will be the amount of worms that can be fed to the fish daily. I provide so much flake food to feed the culture, which the worms will consume more or less within the next 24 hours. It takes maybe a bit of practice to find the right amount of flakes: if there is uneaten food in the culture one day later, we decrease the amount of flakes; if the worms consume everything for the next day but we do not observe good amount of worms, then we increase the portion. If the culture is flourishing, the cover glass will contain only clean worms, not contaminated by the food. If this is the case, I feed the fish directly off the cover glass, by just dipping the piece of glass into the tanks and the worms are washed into the water. From a cover glass of a single culture, I distribute the worms into several tanks. Alternatively, we can wash the worms into a glass of water and rinse it before giving to the fish. Then I feed the culture with flake food, place the cover glass onto the substrate again, and close the lid. I keep the culture damp, so the few drops of water that remains on the cover glass helps to bring continuously a bit of water to the culture every day, and so I do not need to spray any additional water into the box.
The worm culture can run for several months. One of the advantages of the Grindal worm culture is that it should not smell badly, unlike some other live cultures. Every few months, however, it is essential to renew the culture with fresh coconut fibre. I do it usually at the time when I observe that the production starts to slow down, because of waste products accumulating in the culture over time. Additionally, the culture might start to have some smell and, sometimes, small mites would invade the culture. These signs indicate that I need to set up a new culture. If we would not renew the culture at about that time, it would simply crash. I run several cultures in parallel at all times and I recommend having more than one culture on hand.
Brine shrimp
Brine shrimp is a group of about seven species of aquatic crustaceans of the genus Artemia, very often used to provide live food for aquarium fish. Artemia salina was the first that was described in 1758, at that time as Cancer salinus, by Carl Linnaeus in his Systema Naturae. Artemia produces dormant eggs, also known as cysts, which can be stored for long periods and hatched on demand. The freshly hatched nauplii provide convenient form of live feed for larval fish and adult fish of smaller size. In nature, brine shrimps live in salt lakes, and hatching in the fish room should also happen in salt water.
There are a number of methods for hatching the cysts. Following account represent my way, as I do it since many years now.
Brine shrimp eggs are available commercially in aquarium stores or wholesalers. I always try to purchase good quality eggs in 454g vacuum-sealed cans. I store the tightly sealed cans before and after opening in the refrigerator. When I open a can, I take out so much cysts that would be sufficient during the next month or so. I then seal again the can with the rest of the eggs and place back the can in the refrigerator.
For hatching, I use inverted plastic bottles that are filled with salt solution. I use marine salt, without additives, of about 25 parts per thousand solution, which is approximately almost a tablespoon of salt for a litre of water. As my tap water is alkaline, I do not add any buffer. Once the bottle is filled with the salt solution, the desired amount of cysts can be added. I close the bottle with a cap, into which cap a tube is introduced for aeration. Then the bottle will positioned upside down, so the bubbles of the aeration would continuously keep the water and the eggs moving. The bottle is placed into a plastic cup to keep it in vertical position. After adding the eggs to the container, some of the cysts would remain stranded on the side of the container above the waterline, so I might shake the bottle to get all the eggs in the water column.
The hatching time depends largely on the temperature. Egg would complete hatching within at around 26-28 °C. Lower temperatures of around 20 °C will prolong the hatching time up to almost 48 hours, allowing to harvest once a day when employing two hatching bottle.
Various accounts describe that illumination is necessary to trigger the hatching mechanisms of the embryo. The inverted hatching bottles in my setup have only access to normal daylight and I experience very good hatch results, so I do not use additional light sources to illuminate the hatchery. The bubbles of the constant aeration keeps the cysts moving, this is also the advantage of inverted bottles, that cysts and the already hatched nauplii cannot settle down in the narrow bottleneck, from where the aeration is coming. The aeration also provides sufficient oxygen level for the small nauplii, once they are hatched.
Once the nauplii hatched, they can be harvested. The bottles are turned back into the normal position, the cup with the aeration removed. I allow a few minutes for the nauplii to separet from the cysts. The brine shrimp will settle to the bottom and the shells of the cysts would float at the surface. Once the nauplii are clearly separated and gathered at the bottom of the bottle, I open the small valve positioned at the bottom and let the water with the nauplii drained into a fine mesh net. I rinse them in clear water before feeding to the fish. I clear then the plastic bottle to remove the shells of the cysts. I re-use the salty hatching solutions for several weeks, so I re-fill into the hatchery and I add a new portion of eggs.