# Krill and Freshwater Fish



## iamntbatman (Jan 3, 2008)

I know when it comes to using actual fish (or fish flesh) to feed your fish, you should avoid using fish from different climates as feeders for other types of fish, i.e. avoid feeding coldwater fish to tropical fish, and avoid feeding freshwater fish to saltwater fish, etc. 

Does this apply to inverts? I ask because I picked up some frozen krill as a supplement to my Jack Dempsey's diverse diet. He eats any sort of prepared food I feed him, including shrimp pellets, algae wafers, betta pellets (only did this once just to see if he liked them), flakes, sticks and sinking crumbles. His staple diet is Omega One Cichlid Pellets. He also loves frozen brine shrimp, frozen bloodworms, frozen tubifex, live blackworms, live snails, algae I scrape off his walls, pretty much any type of veggie, any sort of live insect (i.e. feeder crickets) and live guppies (home-bred). So, although he gets a really diverse, healthy diet, I thought I'd change his frozen menu a bit. He's getting bigger, and it seems wasteful to feed him stuff like brine shrimp and bloodworms since he eats almost as much in one meal as all of my other fish combined. Krill are pretty big so they seemed like a good step up. Is it safe for him to eat them, or should I worry about the nutrition being off because they're from the ocean? I also fed some smaller krill to my golden wonder killifish and some chopped up pieces to my kribensis and ram - they seemed to like it, too.


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## 1077 (Apr 16, 2008)

I recently tried same with four Discus. Of the four ,only one would eat it. I do not see any harm as treat for freshwater fish such as cichlids. Many fish foods contain it but It prolly wouldn't be good as staple. Also noticed it clouds the water considerably. Corycats seemed to enjoy what Discus didn't eat and that was comforting. (note to self) always try new foods BEFORE water change and gravel vac.:roll:


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## Tyyrlym (Jun 1, 2008)

I'd say try it. If they're just part of the diet and he enjoys them go with it. I'd be more careful if they're a staple.


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## Lupin (Aug 2, 2006)

> I know when it comes to using actual fish (or fish flesh) to feed your fish, you should avoid using fish from different climates as feeders for other types of fish, i.e. avoid feeding coldwater fish to tropical fish, and avoid feeding freshwater fish to saltwater fish, etc.


I have never heard of this. Where did you get this information? Krills are fine for use on cichlids and inverts. Inverts will not pass an opportunity to eat what they can find. They will eat dead fish, other inverts, dead plants, healthy plants (depending on species), fresh meat, etc.


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## iamntbatman (Jan 3, 2008)

I've seen this information in countless places. It seems that feeding goldfish to saltwater or tropical fish is bad because the types of fat found in goldfish are difficult for saltwater and tropical fish to digest and can lead to liver problems. 

By inverts, I meant is it ok for freshwater tropical fish to eat saltwater inverts. I wasn't sure if there would be health issues or malnutrition issues if I did this. Of course, as I said, krill would only be used as a once or twice a week snack for the Dempsey, not as a staple diet.


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## Tyyrlym (Jun 1, 2008)

Well goldfish as feeders is a bad idea usually because of how much fat the goldfish has. This is the first time I've heard someone claim it was the type of fat that was the problem.


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## iamntbatman (Jan 3, 2008)

"A second disadvantage is nutritional imbalance. Goldfish in particular are fatty and are not a healthy staple diet for most piscivorous fish. In the wild, piscivorous fishes will take a wide range of species, some herbivorous, others smaller predators. This means that the piscivorous fish will be able to obtain a correspondingly wide range of nutrients. Simply feeding one species of feeder fish is both unnatural and very likely unhealthy. This problem can, to a degree, be mitigated by "gut loading" feeder fish (see Best Practise, below). By contrast, flake and pellet foods have been carefully formulated to provide a perfect diet for fish. While it might seem monotonous to us, these prepared foods are actually the best all-round diet for most fish."

"A third disadvantage is that some feeder fish (notably goldfish and rosy-red minnows) contain large amounts of the enzyme thiaminase. This breaks down thiamin (vitamin B1) and over time this will lead to serious health problems."

Taken from this thread: Feeder Fish Mini-faq: The Pros And Cons - Tropical Fish Forums

I've seen the reference to thiaminase in goldfish and rosy reds in other places as well. 

It makes perfect sense to me that a predatory fish's digestive system would be adapted to handle the types of chemicals found in prey fish from their own region and that, because of tons of differences in climate and the local flora and fauna, the chemical composition of fish would vary greatly by region.


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