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* This is only a text dump of part of the Aquaria FAQs. * * The web "original" may be more current, is navigatable hypertext, * * and contains enhanced content not available in this posted version! * * http://faq.thekrib.com or http://www.actwin.com/fish/mirror * FAQ: LIVE FOOD contributed by Oleg Kiselev, Don Wilson, and Steve Bartling The advantages of live foods over frozen and prepared foods are: 1. the uneaten food will not immediately decay and load up the filtration system, 2. foods can be raised in controlled conditions and be free of pathogenic (disease causing) bacteria 3. by using inexpensive media and techniques, costs are minimized, and 4. most importantly, fish love grabbing things that try to run away (plus, fish owners love watching their fish chase live food). Here are some live foods the aquarist can easily culture at home, to the extent that some people on the NET have had experience with them. Copyright The FAQs owe their existence to the contributors of the net, and as such it belongs to the readers of rec.aquaria and alt.aquaria. Articles with attributions are copyrighted by their original authors. Copies of the FAQs can be made freely, as long as it is distributed at no charge, and the disclaimers and the copyright notice are included. Contents: * Baby Brine Shrimp * Adult Brine Shrimp * Cyclops * Mosquito Larvae * Blackworms * Grindal Worms * White Worms * Earthworms * Vinegar Eels * Infusoria * Microworms * Fruit Flies * Feeder Fish Baby Brine Shrimp (Artemia spp., usually A. salina) Uses: Baby brine shrimp are a food of choice for the newly hatched fry of egg-layers and other small fish. They're also eaten voraciously by some surprisingly large marine fish and make a good substitute macro-plankton for some filter-feeding invertebrates. Culturing: To hatch brine shrimp, one needs very little. A hatchery can be built out of almost anything, such as 1 gal plastic milk jug to 12 oz soda bottles. Also, stores sell "shrimpolators" and plastic hatching cones. Everything works, but a container with a concave or conical bottom is the best because the water flow has no dead spots. Add air tubing connected to a small pump, put a light over it and keep temperature around 85 degrees if the shrimp are to hatch faster. Ed Warner's book suggests 3.5 table spoons of uniodized salt per gallon of water. He suggests using the cheapest salt available, like the water softener salt at $3 for 50 lb. SF Bay Brand recommends hardening the water to improve hatching and shrimp survival, so adding some Epsom salt and a tiny pinch of baking soda may be a good idea. In order for the shrimp to hatch and not die, the water in the culture must be vigorously turned over to keep the shrimp in suspension. This can be done by aerating the water just like everyone else, using a 12 inch length of rigid air tubing attached to a 3 inch tail of flexible tubing attached to an air pump. The rigid section keeps the hose from slipping out of the container. Aquarists using airstones may find that they crud up and clog too often in this environment. To get nauplii (hatched brine shrimp) out, turn off the air, put a piece of rigid air (1/8") tubing with 2-3 ft of flex tubing attached into the culture, and let the stuff settle. The shrimp egg cases will collect on top of the water, the shrimp ought to sink to the bottom (if the water is not too saline). Then just siphon the wriggling shrimp off into a brine shrimp (fine) net, dump the lot into a cup of water and use an eye dropper to dispense to the fish. The nauplii will live in the tank for up to 24 hours. Sources: Eggs can be bought in most aquarium and pet shops or by mail order. Eggs bought in bulk (such as 1 lb cans) will be much less expensive than the tiny ampoules sold in stores. The cans may be held in the freezer, with 2-3 weeks worth of supply held in a small, tight-lid jar. Ed Warner insists that the eggs of brine shrimp need at least a year of incubation to become ready to hatch. He goes on to say that a low yield from a newly opened can of shrimp eggs may be due to insufficient incubation time and that the best hatches come from the eggs that had been kept for a few years, with the eggs kept for 5 years in a vacuum packed airtight container giving perfect 100% hatch rates. Adult Brine Shrimp Uses: Just about all fish under 5" long will readily eat brine shrimp. Culturing: Don't bother. The yields from the cultures are very low and it's easier to culture Daphnia and buy live brine shrimp in the pet shops. Those who REALLY want to try to culture brine shrimp should get a large open top container (an aquarium, a garden tub, a baby wading pool), fill it with real or synthetic salt water and seed it with some green water and nutrients (fertilizer tabs or what have you) and wait for the water to turn yellow-green. Throw in some baby brine shrimp or live adult shrimp (available from the pet shop) and wait. Adding small amounts of brewers yeast, APR and other micro-foods will help promote the shrimp growth. It helps to put the culture in a brightly indirectly lit place to promote microalgae growth. Sources: See above. Daphnia Uses: Daphnia (also known as "water fleas") are tiny crustaceans of Daphnia pulex and D. magna spp. They are probably the most ideal food for the smaller fresh water -- Daphnia do not die in the tank and will eat microscopic garbage while they live. They come in a variety of sizes -- from hardly visible to over 1/8". This is a typical source of food for many fish in the wild. Culturing: Daphnia can be cultured in everything from betta bowls to 32 gal trash cans. Indoor cultures can be fed various algae scrapings and tank sludge, as well as deactivated brewers yeast, powdered milk and APR (artificial plankton stuff from OSI). The best food to use is green water, and can be used in outdoor cultures. Green water can be grown using a weak solution of Miracle Grow and chelated iron in dechlorinated water, seeded with "pea soup" water. If water full of nutrients is left out in full sun, within weeks it will turn green from the airborne algae spores. Blender-pulverized lettuce is rumored to work well in small amounts. Fry tanks and bowls can be seeded with Daphnia -- the Daphnia eat the bacteria that may be hazardous to the fry and generally purify water and the fry will eat them as they get larger. Freshly hatched fry can also be added directly into Daphnia cultures (about 2 fry/liter) and will feed at their leisure. However, fry kept in equivalent sized tanks and fed more intensively grow faster. A shrimp net or a fine fish net can be used to catch Daphnia. Sources: A clean Daphnia culture may be obtained from a local aquarium club or mail order. Daphnia can also be gathered from local lakes with a plankton net. An inexpensive net can be constructed by the do-it-yourself aquarist. Sew a conical fine mesh net with something like sheer curtain material, and attach it to a circular piece of wire (such as a clothes hanger, bent into a circle). Add some weights to one side of the wire frame and hang it from a three string harness. The net can then be slowly dragged behind a canoe or rowboat in a lake known to contain Daphnia. The wire frame will keep the mouth open, and the weights will act like the tail of a kite, to keep the net from rotating when it is dragged. Such as setup can be remarkably productive, but the aquarist must beware of parasites like Hydra and various carnivorous insects, like glass worms. Capturing glass worms are a mixed blessing, because larger fish will happily eat them, but the glass worms will also eat fry, if present. Cyclops Uses: Same as Daphnia, but predatory. Can damage eggs and very young egg-layer fry. Nauplii can be used like brine shrimp nauplii. Culturing: As Daphnia (but less numerous per the same volume). Sources: Often comes with the culture of worms or as contaminants in Daphnia cultures. Very hard to eradicate once they start breeding in the tank. Also mail order and club auctions, as Daphnia. Mosquito Larvae Uses: Most adult fish of smaller species love them. As long as fish are bigger than the larvae, they'll eat them. Aquatic larvae of flying insects is the main ingredient in the diet of many small fish in the wild. Culturing: Very simple. Put a wide-mouth bucket or a barrel or a tub of water outside. Throw in small amounts of evaporated milk or grass clippings in a nylon bag to seed the water with bacteria and promote the growth of infusoria, mosquito larvae's food sources; green water works well, too. Some people even use manure! If there are mosquitoes in the area, 2-3 weeks later there will be larva in the water. Another means of culturing is to use a child's wading pool with a small amount of grass clippings (no herbicides, please) added to encourage the water to stagnate, then wait for the mosquitoes to breed in it. After a couple of weeks, large numbers of larva can scooped up with a coarse fish net. In this sort of "wild culture", one must sneak up on the pool to net them, so that the larvae don't dive to the bottom when they detect movement. Other methods include filling a one gallon bucket with garden pond water (tap water takes too long to age!), then adding a cup or two of fine soil and allow it to sit for a few days. After the larvae begin to appear, one may use a large aquarium net to strain the water into another bucket, thus capturing the mosquito larvae that are now present. A major problem with these techniques is that the neighbours make take exception to mosquitos being cultured. However, provided all the larvae can be captured and used, an optimist might see it as a means of population control since the mosquitoes are no longer breeding in a pond somewhere where all control is lost. Another problem is that if one adds too many larvae and the fish don't eat them all, there may be a significant increase in the mosquito population in your house, as the uneaten larvae pupate, then develop into mosquitoes. Sources: Wait for the little bloodsuckers to discover the container of evil-smelling bacterial soup (=culture), or go find "floats" of mosquito eggs in a nearby lake or puddle. They look like rafts of eggs, all glued together. Black Worms Uses: These disgusting, bacteria-infested stinkers are among the best sources of protein for the fish and are an excellent conditioning food for breeding preparation. WARNING: frequent feedings will cause the fish to become fat and impair breeding. Also, diseases are far more likely on a steady diet of worms. ANOTHER WARNING: if too many worms are fed to the fish at one time, the worms will burrow into the gravel and hide, risking fouling the tank. Culturing: May not be worth it. Worms will live on the bottom of a tank, eating scum and breeding. They can be fed banana peels. Filter water intensively. Collect them by sieving gravel with worms through a net. Messy, laborious and there are easier sources of protein. Sources: Most aquarium shops have these uglies. (Tubifex are even uglier and stinkier and the aquarist should not attempt to raise them. It is possible, but consider -- they live and feed in sewage and may carry hepatitis or other potential pathogens.) If one buys tubifex, it is reported that since it is their, uh, "food" that smells, not the worms themselves, they may be successfully kept in cold running water without producing odour. Alternatively, 2 oz. of worms can be kept for up to three days in a medium sized bucket of cold water in a fridge). Grindal Worms (very small worms) Uses: These worms are small (up to 1/2") and can be fed to a variety of small fishes. Because of the way they are raised, they are totally disease free. They do not burrow as readily as other worms and live in the water for a few days. Great for bottom feeders and any fish fast enough to grab food sinking to the bottom or smart enough to look for it (i.e. just about all fish). Culturing: Get a plastic shoe box (available at Target on sale for $1), fill it with sterile potting soil and peat moss mix (50-50), or just potting soil, get it moist, perhaps nuke it in the microwave oven for 5 minutes to thoroughly sterilize it, let it cool, inoculate with a small starter culture of worms and add some high protein cereal powder (Gerber, for instance) every time the previous feed disappears -- and watch them breed! Cultures should be kept at 70 F or warmer. Put a piece of glass on the soil and the worms will crawl on it. The worms can be washed off the glass into a cup with clean water and dispensed into the tank with a large medicine dropper (1 tsp). If food is placed in troughs in the soil, the glass will be free of potentially water-clouding soil. One healthy culture produces enough to feed about 100 small fish. Remember to keep the culture moist but not soaked and soupy. Spray it with dechlorinated water now and then. Cultures like this often get over-run with mites and/or gnats. Both pests can be fed to the fish and are readily eaten, but soon become a nuisance. Should this happen, take some worms and keep them in a cup of water for 3-4 hours. This will drown the infestation and the worms can be used as a new starter culture. Old infested cultures can be salvaged, but it may not be worth the effort. If the worms are not growing well, try adjusting the soil's pH by mixing a bit of baking soda into it to neutralize the peat's acidity. An interesting technique of culturing worms is used by some German killi breeders. They use open-celled foam that sits in a tray filled with water and is covered by a piece of glass. This method is cleaner than the soil/peat one. Sources: Friends, local aquarium clubs and mail order. White Worms (small worms, related to earthworms) Uses: These worms are up to 1" long and are good for feeding fish 3"-6" long. Culturing: Similar to Grindal worms, but these worms do not do well at high temperatures. If possible, keep them below 70F; during the summer, they will survive if kept moist and in a cool place, i.e. a north facing carport. White worms can be grown in potting soil in plywood boxes, about 16" x 12" x 6" deep, with a close fitting, moisture-resistant top such as a sheet of glass. They will eat the same foods as Grindal worms, but a number of sources suggest that white bread soaked in milk is a very good food for these worms. Another option found to work extremely well is to raid the materials heading for the compost, and prepare a mixture of old lettuce, fruit, and bread crumbs or oatmeal. Add water and blend it, as thick as the blender can handle, and still be able to turn over this soup. Add maybe a cup each week (it's mostly water anyway, which is needed to keep the cultures moist), in a small trench dug down the center of the dirt. The medium typically and most successfully used by one of us (DW) is dried, rehydrated bread crumbs with some brewers yeast added. Bread crumbs are prepared by collecting old crusts (even moldy ones) and storing them in your freezer, then drying them in the oven at 175F. The bread is then crushed into into crumbs and, if stored in sealed containers (such as plastic ice cream buckets) the crumbs will last forever. When it is time to feed the worms, use a large bowl and mix the powdered bread with enough water to make a slurry, then ladle it into a trench in the culture. Use only as much as the worms will eat in a week. The amount of water in the slurry should be varied - when the worm culture tends to dry out in the summer months, use a wetter mixture to replace the water but if the culture is already too moist, use a drier mixture. One might ask how long such a culture will last before going sour. It is a good question, to which there is no clear answer yet; one of use (DW) has 3+ year old cultures which have been seen to produce as strongly as ever, without odour. Keep these worms in complete darkness. They will come out of the soil and coat the food, devouring it shortly and clustering in a writhing mass. The aquarist can pluck this mass of worms from the soil and use it to feed the fish. The worms will hide in the soil as soon as the light strikes them, so be swift about grabbing them! Another means of separating worms from the dirt is to get a tin can with both ends removed and fasten a piece of plastic window screening over one end (with string, an elastic band, or whatever works). Sit it in some type of tapered glass container (such as a measuring cup) with water in the container, so the can sits above the water (1/2" between the top of the water and bottom of the mesh). Place some of the soil and worm mixture in the can and place a light over top (i.e. a gooseneck lamp, with one of those mini-spot bulbs). The heat will drive the worms out, through the mesh, and into the water. This takes a couple of hours or more. The worms come out clean, and can be fed to the fish directly, placed in a worm feeder, or frozen for future use. This works well for white worms, large and small, so assuming Grindal worms can be grown in soil, it should work for them, too. However, if you don't mind getting your hands dirty, a faster, more effective means of separating them is to put the worm laden dirt into a container, add water, swirl the mixture, then pour out the dirt. The worms will collect in knots. Remove the knots by hand to another container, then continuing to swirl and pour off the dirt in both the old container and the new one. This way, clean worms can be obtained within minutes. Whiteworms should be fed to your fish with a worm feeder, so that the fish can eat them over time. They can be also be placed directly into a bowl on the bottom of the tank, where they will remain until the fish eat them. This may apparently be particularly useful for killifish breeders, which have only peat as a substrate. Be careful not to overfeed by adding whiteworms directly to the tank; the excess will burrow into the sand, where they will be inaccessible to all but the most eager diggers, such as Hoplosternum. Where the aquarist has separated too many worms for one day's feeding, the remainder should be promptly frozen and used later. Sources: same as Grindals. Earthworms Uses: Feeding of medium and large fish (over 4" long). Culturing: To raise earthworms cheaply and easily: 1. Build a box out of wood (any size is fine, a bigger box = more worms) (apartment dwellers can make do with a 1' x 1' x 8" box) 1. Attach the top with two cheap hinges. 2. Drill/cut two 2-inch holes in the front of the box in such a way as to line up the bottom of the hole with the bottom of the inside of the box 3. Paint the box with any outdoor rated, oil based paint. 4. Place a small piece of fine plastic screen against holes that were drilled/cut. Make sure the screen is placed on the inside of the box. Firmly nail the screen into place. The screen will allow the box to drain, but will not allow the worms to escape. The box is now complete. 2. prepare the box for worms 1. Buy enough peat moss from a garden supply store or nursery to fill up the box (remember the peat moss will compact after it gets soaking wet). 2. Place the peat moss in the box and completely soak the peat moss (stir it up until it is uniformly wet). 3. Get 6 bricks. 4. Place one brick at each front corner and two bricks at each rear corner so that the box slopes forward and can drain from the holes. 5. Place a pan under the holes to catch the future runoff (unless the box is placed outside). Note, after worms are growing, the runoff is great for plants. 3. Now, for the worms 1. Go buy three or four boxes of the smallest worms that can be found at a fish and tackle shop. 2. Put the worms in the box 3. Buy some corn meal (a small bag will last forever). This is all the worms need for adequate nutrition. 4. Every three or four days, sprinkle a light layer of corn meal on top of the peat moss. Note: before each new layer is applied, use a small, tined garden hand tool to stir up the peat moss and to mix the corn meal left over from the previous feeding into the peat moss. 5. After about a month, there will be literally millions of worms ranging in size from tiny little young worms to fully adult worms. The baby worms can be used for small fish and very young fish, while the larger worms will easily satisfy the live food requirements of even the most ravenous large fish. 6. This is an infinitely renewable resource, which is difficult to overharvest! 7. The peat moss must be kept damp by periodic watering. Don't over water! Do not allow it to dry out! The worms will die QUICKLY if the peat moss dries out. Fortunately, peat moss retains water very well, and watering is rarely needed. 8. The worms must not be allowed to freeze. The worms and the worm box will not smell and can be kept in garages or closets during the winter. The worms do not like being baked in the full evening sun in the summer (they will be killed). Place them in a shady location if they are left outside. 9. keep the lid closed, worms like it dark. 4. Other uses for Earthworms-- 1. Potted plants love earthworms!! 2. Gardens love earthworms!! 3. Lawns love earthworms!! Sources: the backyard, bait shops, gardening shops, gardens, aquarium clubs. Infusoria (microscopic aquatic protozoans) Uses: Feeding of newly hatched fry. Culturing: Starting with a culture of green or pond water, add plant material such as lettuce, alfalfa pellets, etc. to your culture container. Good results have been found with boiled vegetation, which appears to break down more quickly. When the plant material begins to decay, bacteria will initially appear, then the protozoa will quickly increase in number as they feed on the bacteria. Note that new cultures may contain largely bacteria, not infusoria. If the infusoria culture is vigorously aerated, odour will be minimized. If the aquarist intends to maintain the culture over an extended period, every 3 - 4 days one must siphon out the "expired" organic material which settles to the bottom and discard it, then replace it with new culture media. Optimum culture size depends on how much infusoria is needed. One of us (DW) uses a spare 15 gallon tank, which can produce prodigious amounts of infusoria. An effective means of concentrating the culture before use is to turn off the aerator, then place a small spot lamp beside the culture container and let the culture settle. Within 15 minutes, the infusoria will begin to form shimmering clouds around the light or they may form a distinct whitish layer in the water, often just below the surface. One may be able to see minuscule silvery bits of "dust", moving distinctly and purposefully through the water. The infusoria concentrations may then be selectively siphoned out and added to the fry tank.. Sources: Old tank water (especially out of the filter), friends, mail order Vinegar Eels (Turbatrix aceti aka Anguillula silusiae) Information provided by Greg Frazier Uses: Food for very small fry, i.e., those that are too small to take baby brine shrimp (e.g., Rams) Culturing: Vinegar eels are small nematodes found in unpasturized cider vinegar. They live in acidic water and feed on bacteria in fermenting vinegar. They can survive for extended periods of time in alkaline water (including tank water!), but they will not reproduce. As a food for fry, they are extremely easy to culture, require very little attention or care (i.e., they can be ignored for months at a time), and can be harvested at a moments notice. Hold a starter culture up to the light, to be able to see the worms wriggling in the cider/water mix. To culture vinegar eels, one needs a container (a 1 gallon jug/jar/pitcher with a mouth wide enough to stick one's hand through works well), an apple, cider vinegar and water. Smaller containers should work OK, but a 1 gallon container provides more than enough eels for everything short of a professional hatchery. The cider can be cut by up to 50% with water, but not more than that. Drop some (peeled) apple cubes into the pitcher (one only needs a handful of 1" cubes for a 1 gallon culture), and fill it up with vinegar + water (again, no more than 50% water). Put half of the starter into the culture. Wait at least 24 hrs to give the bacteria time to get a foothold, and then put the second half of the starter into the pitcher. In about a month, a cup dipped into the pitcher should come out cloudy with wriggling worms. When the mixture starts looking really cruddy (e.g., 1/2 inch of stuff has accumulated on the bottom; this should take months) re-culture and start again. Harvest the eels with two cups and a coffee filter. Dip one cup into the culture, pour it through the filter into the other cup, and return the liquid to the culture. Most of the eels will have passed through the filter, but some will have clung to it. Pour fresh water though the filter, then invert the filter and flush the worms into a glass. A filter paper (available at some drug stores) may also be used. Filter paper will prevent any eels from getting through, but it also takes quite a while (10 minutes or longer) for the vinegar get through as well. Let the worms purge themselves in the glass for a while before feeding them to the fry. Also, be careful to rinse the eels well -- adding vinegar to a small fry hatchery could lower the pH suddenly (with disastrous consequences!). Vinegar eels are longer than brine shrimp nauplii, but have a smaller diameter - fish can handle vinegar eels before they can handle freshly hatched brine shrimp. In a tank the worms will flow with any current, but if there is no current they will work their way up to the surface (a big advantage over microworms). Sources: Mail order, aquarium clubs, etc.. Microworms (Nematodes) Uses: These microscopic worms are good for feeding newly hatched fry and the smallest fish, although fish up to 1" or more will eat them. Culturing: Good culture media include Oatmeal pablum, Gerber high-protein cereal or cooked oatmeal porridge. The oatmeal porridge is inexpensive and is the media of choice of one of us (DW). All media should be prepared so that it is thick, then added to a dish so that it is from 1.5 cm. deep or more. Add at least 1 tsp. (5 ml) of deactivated brewers yeast (can be bought from health food stores); the cultures do not do well without the brewers yeast. Seed with a small quantity of the nematodes. If you are subculturing from an existing culture, just use the top 1/8" of the old culture; that's where all the worms are. Your new culture will be encouraged by initially storing it in a warm area (such as the top of a tank). They can be cultured in 500 ml. yogurt containers, made out of type "5" plastic (the type of plastic will be marked in the recycling information on the bottom). This material is fairly thick, flexible, and cheap, and the micro-structure of the surface seems to be such that the worms can crawl up the sides in thick enough concentrations that they can be wiped off and collected. The thinner, more brittle plastic containers work very poorly - the worms do not thrive, and they can't seem to climb up the sides. Cut a hole, perhaps, 3/4" wide in the lid to provide air, and if the cultures are piled several cultures high, ensure the containers are rotated so that all cultures are exposed to the air at least every second day. If this is not done, the cultures will die off. Cultures can be grown in the house, and as many as 24 containers still make up a compact, but very productive source of live food. In about a week, microworms can be "harvested" off the sides of the dish with a finger (the best way), a Q-tip or a brush. Optionally, once can place a flat piece of plastic or wood onto the culture and scrape the worms off with a razor when they become numerous (a popsicle can be used stick as this "collection platform"). Wash them out in a glass of clean water and dump them into the tank, or place them directly in the tank. Cultures will last about 2 weeks. As long as the culture media is fairly fresh, there will not be any offensive odours produced but when the the odour increases and production decreases, it is time to subculture. One can extend the time it takes for the microworms to be passed into the tank by placing them in a worm feeder stuffed with filter floss. Sources: friends, clubs, mail order. Wingless Fruit flies (Drosophila species) Uses: The fruit flies are the closest analog to the natural diet for most killifish and many other small fish. Culturing: 1/2 gal fruit juice bottles can be used as culture containers. The media is a mail order instant mush that seems to be some sort of instant mashed potatoes substance that smells like pure starch mixed with fungicides. Use enough to get a 1/4-1/2" layer of media at the bottom of the bottle and add enough water to get it to a sour cream-like consistency. It should be dense enough to not run when the bottle is tilted. Next, place a 2 layer roll of plastic "bug screen" mesh into the bottle, so the flies and maggots have somewhere to climb out of the wet goo -- it seems to help their survival. Dump in a few fruit flies, perhaps a dozen. Finally, stopper the bottle with a wad of filter floss, so the flies can't get out and wild fruit flies and other critters can't get in. Two weeks later there will be newly hatched fruit flies ready to be fed to the fish. The culture keeps producing for 2 months or so and should be "cloned" after some 6 weeks of operation. When the previously cream-colored media become dark and "used up" looking, it's time for the new culture. It's probably easier and safer to clone the culture every 4-6 weeks and be ready for the eventual crash of the old culture. To feed the fish, sharply shake the bottle to knock the flies away from the stopper, open a fish tank cover, open the bottle, turn it up side down and give it a few taps, shaking out a dozen or more flies every shake. The media gets thick enough by then to not drip out. CAUTION! These flies are wingless and flightless, but not legless. They will walk up the sides of the tank, crawl out through the cracks and head straight for the fruit which has been left out in the kitchen. They may be fish food, but they are still fruit flies. Feed them to fish in small doses. There are several different strains of usable fruit flies. Some are smaller than 1/8", others are over 3/16". Some are completely wingless or have vestigial stubby wings (wingless), others have the wings that are so large that they are useless (flightless). CAUTION! The "wingless" fruit flies will sprout functional wings if they are kept at high temperatures, so keep the culture cool. If this becomes a problem, open the jar outdoors, let the winged flies fly away, then make sure the rest pupate at a cooler temperature. HINT: a jar of Drosophila can be chilled in a refrigerator for a few minutes to make them sluggish and/or immobile. This makes them lots easier to handle when a new batch is being bred, and also makes them less likely to wander off. The fish might prefer them to be more active, though. Feeder Fish Uses: Several large fish, including cichlids and piranhas will eat live fish as part of their diet. Culturing: Generally not necessary. Many fish stores stock offer inexpensive "feeder guppies" or "feeder goldfish" as part of their ordinary stock. However, a colony of prolific cichlids, such as convicts, can practically be used as a source of feeder fry. For fish like piranhas, a small piece of raw chicken or a strip of fish fillet will work just as well as a live fish. Sources: Pet stores; excess brood stock; deformed "culls".