feeder fish dieing

Question
QUESTION: hi. ill just jump right into my question. i have a predator fish tank and i need to feed feeder fish. I have a 20 gal normal tank set up with a decent amount of filtration. in the tank there is usually anywhere from 10-50 rosie reds in there. how come they always seem to die i mean i just bought 50 and now im back down to 10-15 the symptoms are that there are swimming at the top with there heads up and the ones that aren't seem to swim in spurts and spasms. also some have red gills and now some of them have a white fungus over them. Please help soon

ANSWER: Hello,
Your tank is overstocked.  Overstocked tanks bring stress, and disease to fish, and also affect the water quality, bringing death to fish.  There would also be a lack of oxygen.   You never add 50 rosie barbs or any other fish to a tank at once.  You must add two, then wait one week, and if your water chemistry is right, then you add two more, and so on.  Buy a set kit.  Check your ammonia, nitrites, and nitrates.  Ammonia should be zero, Nitrites, zero, and your nitrates must be low.  
A 20 gallon tank cannot hold more than 6 rosie barbs.  They are a peaceful fish, and should never be put in a tank with predators.
Hope this helps
Lynda

---------- FOLLOW-UP ----------

QUESTION: i wasn't talking about rosie barbs i know they shouldn't be put with predators i was talking about rosie red minnows for feeding my preds. roisie reds are  orange color variant from the brown fathead minnow used by pet shops as feeder fish and by bait shops as live bait.

Answer
Hello,
Sorry I misunderstood your question.  You do not have to feed your fish live food.  Earthworms which are cleaned and bought at your bait shop are excellent foods.  To clean them, put them in oats for a week or so.  There are many other foods you can feed them.  Frozen fish that you buy at your market that come from rivers, and lakes are also full of vitamins, and good for your fish.  Unfreeze them first before feeding this to your fish.  Minnows bought at your bait store are also good.  I'm not too sure about buying them at your pet store as many pet stores do not care about them, and therefore some may be full of disease, and if fed to your fish, they would also get the disease.  Crickets bought at your pet store are also a good source of vitamins for your fish.  Frozen foods for fish at the pet store are also very good food for your fish.  
I hope this answers your question.
Lynda