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Dangers of live foods???

Magnum Man

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Jun 21, 2023
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Southern MN
Curious if anyone has run into problems associated with feeding live foods???

I feed Rosy minnows to my Bichir, but I generally try to avoid putting “pet store” fish directly into my tanks…
Other wild critters, coming from sources other than our aquariums… we’ve been getting a ton of rain, and flooding lately, and we have many things holding enough water outside, that mosquito larvae are everywhere, and as much as I’d like to go around with a net, scooping them up, I would think there are risks associated with something coming from another aquatic source…
Even the micro worms, come from dirt or other material, that can hold molds or other things…

Just curious if anyone has had any issues related to feeding live foods???
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Huge issues. If you knew how many times I've passed feeder fish tanks and seen really dangerous infections... Feeders are cheap, and cheap is not cared for or respected. Infected/infested feeders are a huge cause of death for predatory fish. At the price you pay, stores don't spend time and wages on them.

Tubifex worms have a poor reputation as they thrive around sewage.

I have never had problems with live food caught in clean conditions from temporary, fishless pools. No problems with microworms, white or grindal worms, or the usual indoor cultures.
Feeder fish can carry the usual external diseases like protozoan parasites (white spot, velvet, Costia, Chilodonella, Trichodina), fungus, bacterial infections, anchor worm, gill flukes, etc. They can also carry internal diseases like intestinal worms (round and tape), and Fish TB. They can also carry Microsporidian infections in their muscle tissue. Quarantining the fish for a few weeks before using them as food can reduce the risk of external diseases, but unless you deworm the fish you could give your fish worms. And there is no way of treating or telling if a fish has Fish TB until it presents symptoms.

Feeder shrimp can carry some fungus or bacteria on the outside of their bodies but its less common because most pathogens can't get through the shell. However, internal problems can still be spread via shrimp. Intestinal worms, Microsporidian and Fish TB can all be transmitted by shrimp.

Live foods like Daphnia, copepods, ostracods and rotifers that come from ponds/ lakes that have water birds living there will usually carry intestinal worms into your tank. Snails can also do that. If you want Daphnia, either buy some from a lab and culture them at home in containers of green water. Or get some from a pond that dries out during summer and preferably doesn't have water birds living there, then put the Daphnia into a container of green water. After a month you scoop out some of the baby Daphnia and move them into a clean container of green water and let them breed before using them as food. The original wild caught adults can be disposed of.

You can introduce dragonfly and damselfly larvae into tanks if you collect things from natural waterways. Some fish eat them but small fish quite often get eaten by them. These insect larvae can sometimes introduce diseases like round/ flat worms into the tank but they are nowhere near as bad as Daphnia and other smaller crustaceans.

White, grindal and micro worms don't normally introduce anything into aquariums unless the person you got the culture from has Fish TB and adds that water to the worm culture. Then the Mycobacteria can survive in the culture for years and can get into fish when the worms get added to the tank.

Earthworms don't introduce anything to tanks except slime so use small worms that don't need to be cut up for the fish. Small whole earthworms are good food.

Tubifex are normally found in sewerage (as mentioned by Gary) and are not a good food to use.
Blackworms are another aquatic worm that are found in waterways but are normally a lot cleaner than Tubifex. If you get blackworms or Tubifex worms you can culture them in aquariums or containers with a couple of inches of gravel on the bottom and green water. You can add some bottom feeding fish pellets a few times a weeks.

Mosquito larvae living in containers of clean water around the house are fine and make an excellent supplement to a fish's diet. If they are living in an oil slick covered puddle, I would avoid them.

Small flies, moths and other non poisonous insects can be fed to fish and don't normally introduce any diseases. However, some insects can carry pesticide residue on them if they have been exposed recently and most insecticides/ pesticides are highly toxic to fish and other aquatic organisms. If you want to use insects as food, make sure they are free of chemicals.
Part two… so I would assume any processed baked foods, are going to be completely safe, having a “kill step” in the baking, but how about frozen foods, like frozen cubes, or something like freeze dried tubeflex, I assume both types would not have a “kill step” sorry food plant PCQI coming out. With the “kill step” comment…
It would be nice to live where waters don't freeze solid for months, but there are downsides, as Colin described. Here, I collect in snow melt pools in forests - flooded forests, and the ground is dry by August. It cuts down on parasite dangers.

Processed foods are safer, but often lacking. I lost fish to a bloodworm culture I opened, snapped a piece off and fed, then noticed it had thawed at some point. So there's a danger there. Fishfoods are a totally unregulated market though, so there's a risk with some deals. Generally, the food is good.

I've never seen frozen tubifex here.
You are better off cultivating your own live foods so you know they are safe. The only frozen foods I buy, like frozen bloodworms, are from Hikari which advertises being free from harmful parasites and unwanted bacteria.
Mosquito larvae living in containers of clean water around the house are fine and make an excellent supplement to a fish's diet. If they are living in an oil slick covered puddle, I would avoid them.
I wondered about that so looked it up and couldn't find any references to any parasites from mosquitos to fish.

I can feel happy about feeding my fish mosquito larva.
I would only use live food if cultured myself. Feeder Fish is asking for trouble. Just a matter of when, not if. Not directed at you. doesn't matter if they are tetra or guppy. You'd need to QT the feeder for a good few weeks at least.
Part two… so I would assume any processed baked foods, are going to be completely safe, having a “kill step” in the baking, but how about frozen foods, like frozen cubes, or something like freeze dried tubeflex, I assume both types would not have a “kill step” sorry food plant PCQI coming out. With the “kill step” comment…
I know pathogens can still exist dormant in frozen food, but as long as that food is frozen when I take it out the freezer, give it a few minutes, feed to fish, I have a very hard time believing the fish can catch something from that, even if the frozen food has previously thawed before.

You have to assume the frozen food you are feeding your fish has been thawed at some point. That's my assumption. Unless you cultivate your own frozen food!!!

Even blood worm can properly thaw, refreeze and look bright red. I know this from experience. It won't always look brown or different. Same with other frozen fish foods. They don't all necessarily go mushy if they have thawed out previously.
I know that the best foods for many fish are live. But setting aside the disease risks, they can be a lot of work. I know live feeding is even more important that what I did for many years, breeding Hypancistrus plecos. So, I found an acceptable compromise- a mix of frozen and Repashy. I have to buy about 12- 15 lbs of frozen twice/year. The Repashy is a powder one mixes with very hot watter and it gels as it cools. One can make their own custom mixes which is what I did to make a food 80% meat oriented and 20% veggie oriented.

I did hatch BBS for angel fy which was one more reason I didn't breed angels. I also messed around for a bit with red wigglers0 the compost worms. But they have their own issues and as well as they worked I gave them up.

Some years back the NEC had as their keynote presentation after the banquet (which I did not attend) a stage with about well know breeders. I came in late and missed a lot but was there when they answered hte question, "What is your favorite food for conditioning fish?" All of them chose a love food for their answer. The late Rosario LaCorte was on the stage and he listed Tubifex. Black worms, brine shrimp, blood worms were mentioned by the rest. Rosario said that, back when, they collected them in ditches and kept them a while to clean them out and make then safe to feed.

When it comes to frozen the source matters. I tend to use Jehmco for most but there are a few foods they do not handle and I get them online- Hikari and S.F. Bay- mini-blood worms, daphnia, brine shrimp gut load w/ spirulina and some BBS. The slabs I get are mysis shrimp in two different sizes, brine shrimp, cyclops, rotifers and blood worms. I feed different foods to larger fish and and to fry.

My way is much less work for me than live would be for a number of reasons. So I get as close as I can doing the above.

Btw I trust Jemco from whom I buy much of my frozen food and then Hikari and S.F. Bay to be making sure their foods are cultured parasite free.
A little off topic, but not totally… I took back the lil Oscars that were sent to me by accident, to my semi local pet store… I don’t often buy fish, other than some feeders ( usually Rosy Minnows ) and I usually get my frozen foods there… with the holidays, their selection was poor, so I picked up some frozen community blend… I usually mix an assortment, into shrimp cocktail, once or twice a week tonight I tried to add a couple of those community cubes, when I noticed a slip, between the sheets of cubes, that said not to thaw them, before feeding… well they were already in the shaker, when I noticed the note… the cubes did not break up, like the shrimp and blood worms, and dumped out, looking like clay cubes, was my 1st thought… then watching the fish try to eat them, reminded me of Repashi, I’ll have to look them over closer, before next time…
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Part two… so I would assume any processed baked foods, are going to be completely safe, having a “kill step” in the baking, but how about frozen foods, like frozen cubes, or something like freeze dried tubeflex, I assume both types would not have a “kill step” sorry food plant PCQI coming out. With the “kill step” comment…
Cooked foods are fine because the cooking process gets the temperature to 60C or higher and that kills any diseases including Fish TB.

Freeze dried foods can carry bacteria that might become active after the packet is opened and allowed to warm up to room temperature. However, due to the dry nature of freeze dried foods, it will be much harder for bacteria to grow in or on the food and potentially infect the fish.

Frozen foods are usually raw and can contain disease organisms (usually bacteria). Brineshrimp and Mysis shrimp is generally safe because they live in salt water and don't occur in ponds with fish, and most water birds avoid the salty water used to grow brineshrimp.

Frozen Bloodworms, Daphnia, Copepods, etc, can carry bacteria and intestinal worm eggs or larvae. The worm eggs and bacteria can survive freezing. Some companies irradiate the frozen foods and this kills the bacteria and makes the product much safer to use. Products that aren't irradiated can cause problems like internal bacterial infections (dropsy/ bloat).

Frozen prawn/ shrimp and fish can carry external and internal bacteria, Microsporidian, as well as intestinal worm eggs that can survive freezing but not cooking. If you can get the food to 60C for a couple of minutes, it will kill pretty much everything on or in it.

I don't normally use cooked foods for fish but I avoid frozen foods that have not been irradiated and I buy frozen food grade prawn, fish, etc, to use..

The following link has information on cultivating live fish foods.

edited to fix my brain doing one thing and hands typing other things :(
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@Colin_T … was that a typo on freeze drying raising the temperature hot enough to be a kill step, or do they actually heat treat first, then freeze dry ( as I don’t think heating is a part of the actual freeze dry process ) ??? I’m thinking freeze dried brine shrimp and tubeflex worm cubes…

On that frozen food I posted above, I see it also has Gelatin in it, with fish being the number one ingredient…. The cubes didn’t break up in my shaker, so I just dumped them in my Asian tank, out of the shaker, after all the shrimp cocktail had been distributed… my Tin Foils love Repashi soilient green, but didn’t really want anything to do with these cubes, likely because they are more fish based???
I used Gamma irradiated frozen foods frequently. The radiation kills off anything that might become a problem. A quick search shows they are still very much available, here. for example Good stuff.

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