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Grindal
Worms
By: Roger
Winter
Grindal worms are probably one of the most
important cultivated live foods available for both marine and freshwater
fish. They have the advantage of being cheap and easy to cultivate, highly
nutritious and they cannot harbour any aquatic disease or pests. They are
greedily taken by day old fry to large adults of all species and aid in
the growth of new born livebearers. First isolated from white worm
cultures by Mrs Morten Grindal of Sweden who was very active in the
methods of culturing white worms. About half the size of white worms 3/16
- 3/8 inch 0.5 - 1 mm long they are related to earthworms and are normally
much more prolific than white worm. Each individual worm contains the
organs of both sexes and they reproduce in a manner similar to the
earthworm, two worms lay side by side with heads pointing in the opposite
directions, the worms then secrete mucus and when they are covered in a
tube of slime an interchange of sperm is effected. Each worm will now lay
eggs so reproduction is fairly rapid. White worms and Grindal worms occur
naturally in soil but a culture is best obtained from a livefood supplier
(several have web pages see the links page) whom normally advertise in the
small ads in the back of aquarium publications or from a fellow aquarist
who has a culture established.
Before we discuss the method of culture of
these worms it should be pointed out that they do have a few
disadvantages. Some aquarists feel that fish fed exclusively on Grindal
worms become obese due to the fat content of the worms, I have never had
any problems in this area as I do not feed exclusively on worms. I suspect
the problem lies more with the aquarist overfeeding on worms which are
highly nutritious and the fish which are permanently half starved in the
wild become sated and do not exercise by constantly swimming looking for
food, rather that the fats in the worms. Another problem is that the worms
although they can live several days immersed in water cannot swim and so
sink to the bottom were they will dig into the gravel if present to escape
the light. No problem in bare bottom tanks were all will eventually eaten
or siphoned out, nor in tanks with catfish, loach or snails as these will
actively hunt down and devour every worm present. Dead worms can soon foul
a tank so do not overfeed in tanks were large quantities of surplus worms
will foul the gravel bed. Grindal worms are light and strong airation will
keep them in circulation in the water for some time or alternatively use a
worm feeder to feed the fish as few escape the fishes attention this way.
The last problem is that often non aquatic partners often find the
presence of these worm objectionable in the house, (they are completely
harmless by the way) either cultivate them in a shed or garage and allow
for reduced or non production over the winter months or better still put
said partner in the shed or garage thus freeing up more room in the house
for tanks.
Grindal worms can be cultured in plastic
boxes from 250 gram size up to the shallow two litre ice cream tubs.
Obviously the larger the container the longer the culture should last and
remain fresh and productive. The container should be washed and sterilised
and have a tight fitting lid. Pin holes to allow an exchange of air within
the culture, can be either pierced in the lid, or as some culturists
insist around the periphery of the container itself as they maintain this
inhibits the fouling of the culture by flies. The container should now be
two thirds filled with a suitable medium for the worms to live in. The
worms do not like acid soil and peat is too acid unless well boiled to
leach out excess acids, various other mediums such as sterilised garden
loam, African Violet soil, bulb fibre and leaf mould are all used by
various aquarists to culture worms in, each having his own preferred
medium. Indeed this is one area were experimentation is worth doing to
find out what the worms you have prefer. In nature the largest
concentration of worms are found in well rotted vegetable matter as this
is a source high in food. I have had the most success with leaf mould from
a local beech wood that has been used to farm earthworms in for a year
prior to being sterilised and used for the Grindal worms, using it fresh
failed to obtain good results, and the most success with multi-purpose
potting compost (peat based) from garden centre’s used straight out of
the bag. The compost should be damp, too damp and the culture will die off
and smell rather badly, too dry and the worms will burrow deep into the
soil and slow down reproduction. The right degree of dampness is when the
medium can be shaped into a ball that retains its shape but crumbles into
small clumps of material as soon as it is touched with any pressure. Many
different foods have been recommended for Grindal worms and commercial
food is available, the most universally accepted and most successful food
is instant porridge (Readybrek™ in the UK) and on the initial setting up
of a culture a teaspoon to tablespoon dependant on the size of the culture
should be mixed in with the culture medium to encourage the worms to
spread throughout the medium. These instant oats normally have vitamins
added which will pass into the worm and then into the fish. Now introduce
a portion of worms onto the surface of the medium and cover the surface of
the medium with polythene leaving a quarter inch gap all around the edge
of the polythene and the edge of the container to allow the medium to
breathe. Do not feed the culture at this point except by placing a half or
quarter of a boiled potato with the skin still on into the medium. The
skin only should be exposed to the atmosphere to avoid the growth of
mould. All worms shun the light and the containers should be kept in a
shaded position, Grindal worms prefer more warmth than white worms and a
temperature of 680F /200C to 750F / 240F
is required for them to reproduce. Examine the culture daily to ensure
that the food has not gone mouldy or all been eaten. If the food has been
eaten then sprinkle a thin layer of instant porridge over the surface of
the soil and replace the polythene. If all the food has gone the next day
then sprinkle slightly more than previously over the soil if it has not
then do not feed but examine until all the food has gone before feeding
again, remove any food that is developing mould as this will ruin the
culture. Once the culture is well established when you remove the cover
the surface of the medium will be covered with worms and when lifted the
polythene will be covered with worms that can be scraped off with tweezers
or similar and fed directly to the fish. Cultures should be fed daily and
an established culture should be harvested every day as this seems to
encourage the worms to breed. Should the culture start to dry out the
surface of the medium should be dampened either by a fine spray or better
still by a tablespoon to egg cup full of water poured into the centre of
the medium, this gives the worms an opportunity to find the level of
moisture they prefer to deposit the eggs in before it permeates throughout
the medium. It often occurs that you will get a population explosion of
worms after this treatment. Unlike microworms a completely dried out
culture cannot be restarted by the addition of water and must be thrown
away. Food should be applied dry, whilst wet feeding often appears to get
better results this only occurs for a short time before the culture needs
renewing. Any mouldy food should be removed and badly soured cultures
cleaned as described for mites below.
Culture sometime become infested with what
are called mites, these little white insects of about a millimetre in
length are normally springtails which occur naturally in soil. They do not
affect the worms but do compete with them for food and sometimes reach
alarming proportions. If badly infested simply dump the culture into a
container of water and stir vigorously, most, but never all, the mites
will float to the surface and poured off. I always pour of through a fine
mesh net and dump the contents into the tanks as surface feeding fish soon
find and devour them. The remaining water and soil mixture is then poured
through a fine mesh net or nylon stocking and squeezed dry before being
replaced into the container, it will normally take three or four days for
the culture to come on line. I have kept cultures going in a 250gm plastic
fish food container for over two years by only using dry food and the
occasional wash and dry in a fine net.
Never rely on just one culture but set up
two or three just in case you lose a culture for some reason, some
aquarists set up sufficient cultures to fed one day and rest the next,
this is advisable for white worms but Grindal worms seem to reproduce more
quickly if used and fed every day. Once you have a culture going setting
up new ones is a snap, simply set up the container and medium as above
then sprinkle food on the surface and take the worm covered polythene from
the active culture, replace with a new piece and place the worm covered
one on the surface of the new culture. The old culture will be ready to be
used again the next day and the new culture in only two or three normally.
Other infestations do sometimes occur like
little red spiders and fruit flys and occasionally maggots from flies
laying their eggs through the holes in the lid. All can safely be fed to
the fish but in the case of bad infestations it is sometimes more
practical to start a new culture free from pests. Sink the culture in
shallow water so that about half an inch of water is above the level of
the soil. After a while the worms leave the soil and form balls on the
surface of the soil from were they can be collected, thoroughly rinsed and
used to start of a new culture. Dump the old culture medium. If you have
any favourite food recipes or culture mediums or methods for Grindal worms
please let me know so that I may put them on the pages for all to share.
With Permission from
Viviparous |
