[FAQ] Aquaria: Food
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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.
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such it belongs to the readers of rec.aquaria and alt.aquaria.
Articles with attributions are copyrighted by their original authors.
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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".