My husband and I used to look forward to spring when the ice in our “tub” would melt. This tub was actually the lining of an old refrigerator (about 100 gallons) that we kept in our backyard against the garage. As most people thought (at least those who breed fish), spring was the start of serious live food collecting and culturing. Feeding live foods to your fish helps speed up the growth of young fry and helps to condition your fish to spawn much more easily.
In that tub I mentioned above, we collected mosquito larvae (shh, don’t tell our neighbors), daphnia, Cyclops, blood worms, and all sorts of infusoria. Once the weather got colder and the tub froze, the only live foods our fish got on a regular basis were newly hatched brine shrimp for most of the fish and micro worms for the fry. There were other foods we could keep, like white worms and vinegar eels, or sometimes we bought various live foods but that can get expensive.
Just because we are in the depths of a Minnesota winter doesn’t mean we have to restrict the variety of live foods we feed our fish. Take daphnia for instance. Daphnia was first described in 1669 by Jan Swannnerdam from Amsterdam (I swear this is true. I didn’t make this up). Jan gave this water flea the Name of Putex aquatiticus arborescent but are more well known today under their current name of Daphnia sp. And there are more than one species but they are all wonderful live foods.
So long as the pond is not frozen solid there will be daphnia – of course, you will have to break through the ice first. Daphnia like to hang out around objects in the water, next to floating (or frozen) logs, large rocks, etc. so don’t just swish your net around in open water and expect to get loads of daphnia. Swish your net around objects then clean it out in another bucket of water – the same water as that which is in the pond to prevent the daphnia from going into shock because of drastic temperature changes. When you have enough daphnia, take it all home and either feed it to some lucky fish or feed some and keep some.
Daphnia is cultured by placing them in a tank or bucket of aged and treated water and kept as cool as possible. According to the Encyclopedia of Live Foods, sheep or horse manure is recommended as an excellent food to feed to daphnia. Personally, I have no idea how to get sheep or horse manure, short of going to my uncle’s farm in Wisconsin (I could just imagine myself trying to explain this to him), and I truly have no wish to find out how. I have found that crumbled up dried leaves will keep a culture alive but will not have it growing to the point of being able to feed any. Adding dried yeast helps but is still not quite enough. A mixture of chopped lettuce, cooked oatmeal, wheat bran, and even pieces of the raw liver (sound yummy?) will give you a culture where you could feed on every week or so. Experiment a little to find out what works best for you.
Glassworms are another good live food for the winter months. Although called a womm, they are actually a nidge (or larvae) of the biting gnat, Chaoborus plumicornia. The adults closely resemble mosquitoes but whereas mosquitoes have scaly wings, C. plumicornia have hairy wings (check closely, now, the next time you’re inclined to swat that “mosquito”). They also do not suck blood and the larvae will, in fact, eagerly devour mosquito larvae if given the chance.
Glassworms have been known to hang out with daphnia so when collecting, you may find them both in the same place (wouldn’t that be nice) but just because you find daphnia doesn’t necessarily mean you will find glassworms. If you managed to come across a supply of glassworms in the late fall, before all Minnesota freezes over, from a source that will not freeze solid in the winter, you may be in luck. As was mentioned by Harvey Moore of Calquarium:
There is nothing more disappointing than to chop through two feet of ice only to find there are no glassworms. It is even more disheartening to chop through the ice and find nothing but mud.
I will assume that you do not already have a pond or lake that is a reliable winter source for glassworms. What to look for as a hopeful source of glassworms is an area on a lake or pond (that you think is not frozen solid) that is shaded through most of the day, probably has a low oxygen content, high carbon dioxide content, and the presence of hydrogen sulfide. In other words, someplace with loads of dead and decaying matter at the bottom. When you get through the ice to (hopefully) water, take your collecting net and start slowly swirling it around in the water. If you hit pay dirt (and not mud), the glassworms will look like a clear mass of squirming jelly in the net. Dump the mass in a bucket of water that you pulled from the pond or lake (because, like daphnia, they could die from shock caused by severe temperature change) and continue until you have enough for your needs.
You can’t really culture glassworms because they reproduce in gnat form which means they will grow wings and fly around the house. And because they look so much like mosquitoes, before long nobody will want to visit you because they won’t know the difference. They can, though, be kept in larvae form by keeping them real cold — for example, in the refrigerator. Be sure to change the water every day or so.
Now this very important: Glassworms are not fry food. Use them only to condition your adults. Remember when I mentioned that glassworms will devour mosquito larvae if given a chance? Well, glasswonns are predatory and will also, in fact, eat the small fry. They have also been reported going after fish eggs so be careful not to overfeed them to fish expected to spawn soon. The only exception to not feeding glassworms to fry I can think of is the fry of the pike livebearer, Belonesox belizanus. These fries are born fairly large (about one inch) and are extremely predatory themselves. Although they can hold their own against glassworms (and, in fact, the glassworms were a welcome emergency food for the fry) the glassworms were seen trying to “pinch” the Belonesox.
An important thing to keep in mind while collecting these foods is to stay aware of your own safety. People fall through the ice every year and you don’t want to be one of them. Make sure the ice is thick enough to support your weight. To be safe, when the o.k. is given for ice fishermen, then you have it also. But when their time is through for the winter, so is yours.
If you don’t feel quite so enthusiastic about digging a whole through a couple of feet of ice in freezing cold weather just to give your fish some live food, you’re not the only one. There are still cultures of live foods that can be kept year-round. Why not try to keep micro worms, white worms, vinegar eels, mealworms, brine shrimp, or any of the other cultures available? To learn more about collecting and culturing live foods for your fish, I recommend the Encyclopedia of Live Foods by Charles O. Masters. This book is currently out of print but can still be found at several of the used and out of print book stores that specialize in aquarium literature.
Encyclopedia of Live Foods. Charles 0. Masters. TFH, 1985.
Foods for Tropical Fish. Glassworms by Harvey Moore. Calquarium.
Foods for Tropical Fish. Suggestions on Glass Worms by R. Lister. Aireborough & District Aquarist Society.