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FAQs on the Rainbowfishes Foods/Feeding/Nutrition

Related Articles: Rainbowfishes Fishes at the rainbow's end;  An introduction to the Atheriniformes, the rainbowfish and silversides by Neale Monks

Related FAQs:  Rainbowfishes 1, Rainbowfishes 2, & FAQs on: Rainbow Identification, Rainbow Behavior, Rainbow Compatibility, Rainbow Selection, Rainbow Systems, Rainbow Disease, Rainbow Reproduction,


Millennium Rainbows Emaciated      7/13/14
Hello WWM! I’m wondering if you can help me out on an issue I’ve been witnessing with my Millennium Rainbow's I bought five months ago… One male, one female. Both were roughly two inches at purchase and filled out well and healthy looking, but now, five months later, as all my other varieties of Rainbow’s have grown fat and happy, those two have grown thin, sickly in appearance, and drastically lost color. None of the other fish display similar issues and the Millennium’s are not harassed by the other fish. Here is what I currently keep in my 55 gallon tank:
2 millennium rainbows (one male, one female)
2 turquoise rainbows (one male, one female)
3 yellow turquoise (one male, two female)
2 Australian splendida rainbows (one male, one female)
1 Synodontis lace catfish
Temp stays at 74 degrees F
Nitrates/Ammonia all ok (regular 30%-50% water changes weekly, as Rainbows prefer)
PH 7.0
From start-up, I used 4 Neon Blue Dwarf Gouramis and my Synodontis Lace (whom so desperately needed out of the 30 gallon) to cycle to the tank. After 3 weeks, I then added all of my above fish, except for the Yellow Rainbows. Then, after another 2 weeks, I removed the Gouramis (took them back to the fish store) and picked up the three Yellow Rainbows. During this time, I only fed Tetra Color flake food to the rainbows and all of them ate it without issue. It was when I brought home the Yellow Rainbows, that I began to feed frozen bloodworms. I believe I may have ‘over-did it’ with the bloodworms, as I fed them a cube and a half total per day, spaced out over three feedings. My ex, (whom was a manager for a big name fish store in the area for 23 years) scolded me for feeding them so much, and said I needed to focus more on flake food, and cut back to feeding one or two times a day. So I did…
But then I noticed that the Millennium Rainbows had no interest in the flake food, (which became breakfast) and would hold out until I fed the 1/2 cube of bloodworms (which became dinner). They simply shot the flake food right back out of their mouths, and then began to not even ’taste’ it at all, practically turning their noses up at it, so to speak. I was told by everyone that they would “come around and start eating the flake food again”, but even after 4 weeks of this routine, they did not. It felt all wrong not feeding them like I was before. It was during this time that I noticed they began getting thinner.
Then, at 9 weeks, I thought that some of my rainbows had developed 'mouth rot’, a white fluffy fungus on their lips. It seemingly bounced from one fish to another. I first treated with a cheap mainstream fungus cure, that turned my water a horrendous radioactive green. I used active carbon after the appropriate time, cleared the tank and waited. The white ’stuff’ continued to appear randomly on my fish. I was told by the fish store that my tank was in ‘dire straights’ and needed Seachem Sulfathiazole. I followed the directions. Nothing changed. Later, I discovered via the web, that rainbows can damage their lips by bumping into things, etc. and I took the chance that that was the problem and stopped dosing my tanks. Lo’ and behold, within 2 weeks, the problem never worsened and eventually disappeared.
At this point, my tank was 12 weeks old. All fish were doing very well, but my Millennium’s were drastically thinner, their color gradually fading, especially in the male. They were the slowest in the tank now, hovering in the corner together, never moving except at feeding time, and their poop began to turn clear. I decided to go back to feeding bloodworms multiple times a day, as I was before, to see if they fattened back up... But to no avail. I even added beef heart and brine shrimp on occasion, and still offered flake food for the other fish, and while they ate whatever I put in the water, the two Millenniums STILL only ate bloodworms.
Now, I’m at the five month mark, and all the rainbows have grown exponentially, but the two Millenniums look like ‘death warmed over’. Their activity HAS increased, as they both now swim with rest of the school since I went back to feeding them bloodworms more often, but the once golden female is now a horrid brownish yellow and the once brilliant red male is a silvery, faded pink. He doesn’t even flare his fins like he used to, instead opting to keep them laid tight to his body, making him look almost identical to the female. Their poop now at least has color to it again, instead of being clear-ish, yet both of them are an entire inch smaller than all the other rainbows and even more shockingly thin. The males of my rainbows are all beginning to have the pronounced ‘big body/little face’ appearance, yet the male Millennium is still straight and narrow, like a female.
I’m at a loss. Is this common? Do Millenniums have a history of being picky eaters? What could be causing their emaciated appearance?
I just added another male Millennium today, which is what prompted my question, because the newcomer is a brilliant red and fat and happy… He makes my other two look even more like they have one fin in the grave. And so far, he eats the flake food when offered. None of my other rainbows show the slightest signs of illness. Where did I go wrong with those two? Could the medications from before have been a factor? Or is it an issue with their eating habits?
And am I over-feeding at 3 times per day, with 1 and 1/2 cubes of frozen food total per day, even though my tank stays clean and balanced? I’ll take any suggestions or thoughts on the matter at this point. Thanks so very much for your time.
<Greetings. My gut feeling here is Mycobacteriosis, which is a problem with Rainbowfish. Not a common one, but a persistent one. The big issue Mycobacteria is that they're effectively untreatable. You can do quite a lot to prevent them causing sickness, but once they're there, your fish are pretty much dead men walking. Mycobacteria are potentially contagious too, though it's hard to quantify this because environment seems to trigger Mycobacteria infections that are latent (i.e., there, but harmless) in aquaria generally, so it's difficult to say if the second fish was infected by the first or merely succumbed to poor environmental conditions later than the first fish. Make sense? Worms are also a risk, as with any tropical fish, but compared to Mycobacteria they're a lot easier to treat using a proprietary antihelminthic medication (such as PraziPro) and you might do this anyway, so you can tick off this possible problem. Anyway, Since your aquarium is relatively young, evaluating and disregarding environmental factors causing ill health will be the first step. Rainbowfish are fairly adaptable, but for the most part they appreciate neutral water that isn't too hard or too soft, so review water chemistry. Most don't like extremely of temperature either. Likewise, water circulation should be brisk but neither sluggish nor turbulent, and oxygenation should be high (which is one reason not to overstock their tank or keep it too warm). Diet is always a factor to review; good quality flake is ideal, but as you seem to realise, bloodworms are kind of like Chicken MacNuggets but for fish -- readily eaten, but not sufficient by themselves. On the other hand, underfeeding Rainbowfish is easily done; they seem to have large appetites and perhaps limited ability to store nutrients, so frequent small meals are better than one or two big meals. It's also possible you got a bad batch of bloodworms; indeed, some aquarists I know refuse to use them at all, citing the conditions they're reared in as proof enough of their inappropriateness as aquarium fish food. I will direct you now to the www.rainbowfish.info website, among whose members is Adrian Tappin, one of the foremost experts on this group of fish. They may be able to offer you a second opinion. Cheers, Neale.>

Rainbows choosing not to eat?   6/22/11
Hi all.
I have some questions relating to the dwarf neon rainbowfish, Melanotaenia praecox. I purchased four of these fish (two males, two females) and put them into a 29 gallon tank that has been set up for about a month and is fully cycled (see water quality and decoration details below). Existing tank inhabitants are six Corydoras aeneus.
These rainbowfish have been in the tanks since Sunday afternoon, and it is now Tuesday evening. During that time, I have tried feeding them two different varieties of flake food (Aqueon tropical flakes and Tetra Color Tropical Flakes), both of which are fresh, not stale. I have also tried feeding them freeze dried bloodworms (Tetra brand), which I just purchased and opened tonight. The fish don't seem to notice the flakes or bloodworms on the surface, but as they sink to their level they go grab them readily enough, getting entire pieces into their mouths and then closing their mouths, sometimes for as long as five seconds. But then they invariably spit them out. The flakes/worms look about the same size when spit out as they did when they went into their mouths, so I'm not sure if they have swallowed anything at all since I've gotten them. Can you think of any explanation? Eventually the foods gets to the aquarium floor where the Corys attack it, so I'm sure they aren't getting anything later when I'm not watching. I called the fish store and asked what they've been feeding this fish, initially thinking they were just finicky, and they told me flake food and bloodworms, so I'm really perplexed by this behavior. I guess I maybe should have asked whether those bloodworms were live, frozen or freeze dried, and more details about the flake food (they said it was their store brand), but it still seems strange they won't eat two brands of fresh flake food or freeze dried bloodworms.
<Indeed, but sometimes fish are picky. Wet-frozen bloodworms are usually very good at tempting new fish to eat. Live brine shrimp and daphnia are also very good, but watch they don't get sucked into the filter -- if you want, switch off filters for a few minutes while they're feeding.>
Otherwise, these rainbows appear perfectly fine. They are beautiful with great coloration, no signs of disease, and they swim around the tank normally. They were shy at first and spent a lot of time hiding in the plants, but I am starting to see them more often in the open area now so they appear to have mostly overcome that.
I have Googled other sites and read many of your FAQs, but can't seem to find anyone with this problem. Most describe them as greedy eaters of flake food. Any advice would be appreciated, as I would really hate to lose these beautiful fish due to inexplicable starvation.
Tank & Water Quality Data:
Ammonia: 0 ppm
Nitrites: 0 ppm
Ph: 8.0
General Hardness: 12 degrees hardness
Carbonate Hardness: 15 degrees hardness
Temperature: 74-75 degrees F
Substrate: Small size rounded aquarium gravel
Decorations: Many artificial silk plants, one real piece of Mopani wood
Filtration: Emperor 280 filter with Biowheel, and the normal filter cartridge (floss/carbon). Also weekly 25-33% water changes are done.
Thanks for your help!
<All sounds fine. Fish will go off their food when stressed, so keep an open mind. Otherwise don't feed for a few days, and then offer some food.
Cheers, Neale.>

Madagascar Rainbows Won't Eat Dear Friend <Good morning to you my friend> I have an urgent question - I have recently bought some Madagascar Rainbows - they looked well at the store but since then they have little interest in what I am feeding them. I read that they would take flakes. After they did not, I tried dried bloodworms and later frozen bloodworms. These do not seem to interest them. Three of them just died, no doubt by starvation. <You might try feeding them small live foods. Small fishes (if you're sure they're disease free) or live worms such as bloodworms. Sometimes even small earthworms will entice finicky eaters.> Kindly help. Thank You. Faris <You're welcome! Ronni>

Bloodworms for Rainbows  8/25/06 Hello, <<Hi, April. Glad to have you back! Tom here again.>> I need some expert advice that I have not been able to get at the pet store and haven't found searching the internet.  Can you help? <<You know I'll try.>> Here it is: I have 7 threadfin Rainbowfish (Iriatherina werneri).  Three males and 4 females.   <<Very nice choice, April.>> I had planned on getting more, but the LFS was "closing them out". The males were added first and hid and shook for 4 days before coming out. The females were just added 5 days ago and you should have seen the males change.  They were parading around the females and even changing colors.   Very pretty and impressive. <<Boys are definitely show-offs regardless of the species. :)>> Okay, the question.  I bought frozen bloodworms as this is what they were getting at the store along with flakes.  The package has separated cubes to defrost and feed.  The problem is this is way too much.  I just today put a few in the tank and they seemed to like them.   I read that this species has small throats and food has to be small.  Do I need to cut the worms smaller (yuck)?   <<The worms will be soft enough for the fish to chew what they can of them. I wouldn't be concerned about this aspect.>> How long can I keep the rest of the defrosted worms in the fridge?   <<Personally, April, I wouldn't store these for more than a few days at most.>> I did plan to feed the bloodworms once a week.   <<A couple of times a week won't hurt at all. They're a good supplemental food source.>> With people food I don't keep in the fridge longer than 4 days.  So I wonder if I should give a few more in 4 days then toss the rest? <<Wasteful as it seems, this strikes me as the best course of action, April.>>   I also thought it a good idea to feed the worms the day prior to or the day of cleaning/water change to get rid of the uneaten worms. <<An excellent plan in my opinion.>>    I read about the foods that Rainbowfish like in general, but due the threadfins smaller size, do you know of better food choices? <<Not better but you might consider frozen brine shrimp, as well. Small enough, I should say, and also a good supplement. The downside is that it brings us right back to the "problem" with over-supply. One thought would be to see if it's possible to snap one of the cubes in half with a sharp knife, preferably without shooting a chunk of frozen bloodworms through the kitchen window. :) The future alternative would be to go with the freeze-dried variety, the smallest container you can find. Freeze-dried foods lose none of their original nutritional value and would eliminate the waste. As for purchasing small containers of food, I recommend this because the food goes stale after a time. I don't hold on to any of mine for more than three months before pitching it out and buying new stuff for my guys.>> P.S.  I want to thank you again for your previous help when I lost the first fish to ICH.  I waited, tested and researched before purchasing these threadfin Rainbowfish.  I really was ready to just give up with the whole aquarium deal.  But thanks to your help and encouragement, I have a nice healthy tank with beautiful fish.  I couldn't have done it without you. <<If I were having a bad day up until now, that's over with, April. I can't think of a nicer compliment and I pass that on for all of us here at WWM. Thank you.>>   Tom, I changed my mind about the "blue Rainbowfish" (8/6/06) since they didn't know or want to know what the scientific name was.  Got me worrying about how big they would really get and how healthy they were. <<Well done. Actually, it's, legitimately, Melanotaenia praecox. Provided there's been no "tampering", these would have been a good acquisition but, between you and me, I like the Threadfins better. My best to you and the whole "crew", April. Tom>>  

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