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FAQs on the Rainbowfishes Systems

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 Feeding, Rainbow Disease, Rainbow Reproduction,


"Water changes. Rainbowfish REALLY like water changes. I typically perform 50% water changes on my fish (weekly suggested but at least 1x every 2 weeks) and they really enjoy this. 10-20% weekly changes really just doesn't get the job done. Hardness, pH On the GH side anywhere between 100 ppm - 250 is fine for them. Harder is ok too but they get tougher to breed and the eggs sometimes don't hatch at the higher hardness values. On the KH end I feel that it is extremely important to get at least 3-4 degrees of carbonate hardness here. If you have softer water supplement it by adding baking soda, sodium bicarbonate. In my water a tablespoon in ~ 55 gallons increases by about 1 degree KH. pH bounce is something that really stresses Rainbowfish and if present can cause them to get TB. Most of the Rainbowfish people have pretty well discounted the other wasting diseases. TB is not easy to test for but when it has been done - skin ulcers, mouth ulcers, bloating (shot kidneys) and wasting have all been positive for TB." Excerpted from a note in by Gary Lange

Boesemanni rainbow community tank- 8/20/11
Good Evening-
<Hello Sea,>
Hope you are well. I greatly appreciate the hard work you put into maintaining WWM as a great resource to both novice and experienced aquarists.
<Thanks for the kind words.>
I have a question involving stocking, planning for future growth of juvenile fish and the actual projected adult size of my fish. I have a 75 gallon, heavily planted freshwater community aquarium with EI dosing and DIY CO2. My temperature is 76, PH at 7-7.2, KH is 10 and GH of 14.
<Sounds good.>
In February of this year (2011), I purchased some Boesemanni Rainbow fish from a breeder via the internet-I purchased 10 and received 13.
The plan was for them to join my; yellow Gourami, 5 Brochis Splendens (best fish ever!),
<Agree; charming, underrated fish, perhaps even better than Corydoras for medium-sized community tanks.>
5 Giant Danios, 7 Otos, 100 or so red cherry shrimp and 2 Amano shrimp which they did. It was winter when I purchased them, so I ordered 10 assuming I would get 8 or 9 after shipping casualties (had never purchased fish in that manner before, and read that casualties should be planned for).
<Actually, less of an issue than many expect. Most of the fish we buy are air-freighted, and provided the seller knows what they're doing, and you don't choose species that ship poorly, you should do well with this approach.>
The seller shipped an extra 3 and they all survived, putting me +5 fish.
When I got them, they were but a few months old, still unsexed and bland in color.
<Absolutely standard with Rainbows.>
It looks like they are 3 females and 10 males (not the ratio I was hoping for) and there is a bit of a size difference between the largest and the smallest.
<I see.>
The rainbows are starting to get a bit larger, the largest being 2.5 inches or so but most in the 2 inch range.
<Still babies.>
Currently I am not having any issues-all my fish are getting along and my water quality is top notch. What is the actual adult size I can expect for the Rainbows-the information on the web isn't very consistent?
<Oh, realistically a good 10 cm/4 inches, but occasional specimens do get bigger. Wild-caught specimens tend to be bigger and more colourful than farmed ones. I have seen some nearer 12 cm/5 inches.>
Likewise, my giant Danios and Gourami have not really lived up to maximum sizes listed on most sites-they are all about 3-3.5 inches and I have had them for nearly 2 years. I have seen estimates on max size for all 3 (Danio, rainbow and Gourami) species maxing out at 6 inches.
<Six-inch Giant Danios are really very uncommon. Farms tend to breed from specimens that reach sexual maturity quickly, and these are often smaller than average specimens. So over the generations, farmed fish tend to be smaller than wild specimens. In the wild, only the biggest specimens have the strongest genes, and so they're the ones that breed the most. So you get the opposite thing there, selection in favour of big, strong specimens rather than small but precocious ones. There are some exceptions here, notably among the Mbuna cichlids that live longer and eat better in captivity than in the wild, so they're often bigger than in the wild. But almost everything else is smaller in captivity once it's been farmed for a few generations.>
What are your thoughts on the eventual growth I can expect from my fish, specifically the rainbows, and do you have any recommendations on how I should adjust my stocking for future success?
<Oh, I think you have good ideas already. The Rainbowfish/Gourami combination works well, and I've seen things like Lace Gouramis and Moonlight Gouramis work particularly well. Is there any particular type of fish you'd like to keep?>
My original plan was to add a school of 4f and 4m rainbows to my existing livestock, but I am now 5 fish richer then I planned for. I doubt upgrading to a 90 gallon tank would provide much benefit, and I don't think I am in a position to start from scratch and spend all of the money that would come with upgrading all of my lighting, stand etc to get a 6ft long tank. Thanks much for your help!
P.S. here is a link to full details on my tank with pics:
<Cheers, Neale.>
Re: Boesemanni rainbow community tank- 8/20/11
Thanks Neale. I have no intention of adding any additional fish-just don't want to end up too crowded with the fish in there right now. I figured that I would be pushing the bio-load limit a bit, but I am glad to know I
will be within reason at adult sizes. I appreciate your analysis and help.
<I see. I don't think you're overstocked yet. Good luck! Cheers, Neale.>

Boesemani Rainbowfish in sg 1.003 tank?  11/15/10
This is my second question in a week. I don't want to abuse this wonderful resource, but I do have another question.
I have a Rainbowfish that looks to be a Lake Kutubu Rainbowfish (my knowledge of Rainbowfish is pretty limited, though I have read your articles on the WWM site). Its other Rainbowfish "friends" died over the
past year; I'm pretty sure the deaths were from Columnaris.
He is in a tank that has softer water and a lower ph than I now know Rainbowfish prefer.
Could he thrive in a 90 gallon, low-end brackish tank, sg 1.003, ph 7.8 with an Archer (Toxotes jaculatrix) and a spiny eel (tyre track)?
If so, I would want to buy more of his species and create a proper school for him.
Thanks for your thoughts on this.
<Hello Laura. As a very general rule, Melanotaenia species from hard, alkaline water environments will do well at low specific gravities, even if they don't naturally come from brackish water habitats -- off the top of my head, the only Melanotaenia species that I can recall coming from brackish water in the wild is M. nigrofasciata. In any case, Melanotaenia lacustris and Melanotaenia boesemani need hard, basic water anyway, and the addition of very small amounts of salt should do them no harm at all. I'd be keeping
the tank at 10% seawater salinity, i.e., 3.5 grammes/litre, or about SG 1.002. My guess would be that your Rainbowfish will thrive kept in such conditions. Archerfish aren't fussy about salinity at all, and Spiny Eels need fairly low salinity conditions, so reducing the salinity shouldn't cause problems. Cheers, Neale.>
Re: Boesemani Rainbowfish in sg 1.003 tank?  11/15/10
Thanks, Neale--that's great news.
By the way, I saw your book on brackish fish at my favorite fish store in Manhattan over the weekend.
<Ah, and if you look in the Australian Fish chapter, you'll see quite a bit about Rainbowfish in brackish water systems!>
It took me by surprise and I nearly squealed in delight when I saw your name. I told the manager that I had had a back-and-forth with you through the WWM website. I don't know if he quite grasped the importance of the moment (!), but I was impressed. Anyway, I know that book is going to be on my Christmas list!
<God bless Santa Claus!>
<Cheers, Neale.>

Re: Boesemani Rainbowfish in sg 1.003 tank?   11/24/10

Hi, Neale,
I had to give you an update on my Blue Rainbowfish.
Since I put him in the 90 gallon low-brackish tank he's a different fish!
His color is so intense and beautiful and he has a bright neon band of yellow (I have never seen this before) on his dorsal line (don't know the technical term but that's as good as I can do).
I got him some Rainbowfish friends (6) and he immediately (and I mean didn't skip a beat) started courting all the females. In fact, I think all but one is a female because he's very aggressive with only one of the fish.
The tank is big and I have it heavily planted but the fish that he is attacking doesn't try to hide. If the fish was suffering would it hide?
The most amazing thing just happened--I went to take a photo of my beautiful fish to attach to this email. I had turned out the lights about a half an hour ago. When I turned on the light I couldn't find him, then I
saw him: pitch black!!!! Absolutely black as night! I didn't know they changed color like that. Wow--that is so cool!
<Glad your fish have responded so well to the slightly brackish conditions.
While not essential by any means, many aquarists have found that under home aquarium conditions the addition of small amounts of marine salt mix is beneficial to Rainbowfish. Anyway, yes, males are aggressive towards one another, though rarely to the point of causing harm unless the tank is too small. Having lots of females causes male Rainbowfish to exhibit extremely bright colours, and when people buy just males they lose out on some of the best colours you'll see on male rainbows. And yes, rainbows change colour at night. Many other fish do, too, so it's worth keeping an eye out for.
Pencilfish are famous for this, as are neon tetras. Cheers, Neale.>

Australian rainbow fish, hlth., env.      12/19/09
I am writing concerning one of my rainbows. I have 55 gal. freshwater aquarium with 15 fish 6 of which are rainbows.
<All one species, I hope. Australian Rainbowfish are not only schooling fish, but also prone to bullying one another if insufficient numbers. Keep at least six of each species, and don't mix species of radically different sizes. Make sure there are equal numbers of females and males (or better yet, more females than males).>
My perimeters are Ph-7.0-7.2, Ammon.-0, No2-0 and No3-10, with weekly water changes.
<Fine. But what about water hardness? Rainbowfish on the whole come from either soft water habitats or hard water habitats depending on the species.
A good all-around option would be medium hard water (~10 degrees dH) and neutral to slightly basic pH (7 to 7.5).>
Two days ago I noticed one the rainbows swimming almost vertical with head down and tail up. He is also using his whole body in a wiggly motion as he swims. There are no spots or marks on him and he is eating fine. At times
he looks like he doesn't know where he is swimming to because he almost bumps into other fish.
<Doesn't sound good. Review water chemistry and water quality. Check for potential sources of poisons: insect sprays, paint fumes, children doing stupid stuff like putting soda pop into the aquarium (happens). Make sure
the food you are offering is adequate. Flake, pellet and freeze-dried foods are fine up to a point, but they tend to cause constipation if used on their own, and in some cases this can lead to swimming problems (I guess the extra weight inside them messes up their buoyancy). A mix of quality flake with wet-frozen bloodworms and mosquito larvae, plus live brine shrimp and daphnia would be a good balanced diet. Live brine shrimp and daphnia are laxatives, so highly recommended for all small fish now and again.>
Is this cause for concern-something internal---parasite-etc.
<Most likely caused by the environment (i.e., the aquarium) rather than a mystery parasite; while there are Whirling Disease parasites, they have complex life cycles that can't be completed in aquaria, so usually affect only pond fish. Live tubifex can introduce them though, but I don't think anyone uses live tubifex anymore.>
Need for quarantine?
<Would likely kill a schooling fish like a Rainbowfish. Much better to identify the possible source of problems, and fix the aquarium. Even though you have zero ammonia and nitrite, be open minded about this aspect, and think about whether there could be other problems like unstable pH or inadequate oxygen distribution throughout the tank that could be to blame.>
I would appreciate any info you can give me.
Thank you for your time,
<Cheers, Neale.>

Rainbow fish.. Sys.  -- 6/17/09
Hello crew,
I was just reading this article
<http://www.wetwebmedia.com/FWsubwebindex/atheriniforms.htm> by Neale about rainbow fishes, because I've been investigating setting up a brackish system with some Melanotaenia boesemanni. I know some rainbows do well in brackish and some do not, and was wondering about these.
<They'll do fine in slightly saline conditions, up to around 1.003 at 25 degrees C. They aren't brackish water specialists though; of the traded species, only Melanotaenia nigrans is a true brackish water specialist, and
it certainly does well to around 1.005 at 25 degrees C.>
Also, I was going to set the system up in a 29G tall tank, but read they might need more swimming room than that, and wanted to get an opinion from the experts.
<Certainly these medium- to large-sized rainbows will need a tank upwards of 1 metre/36 inches in length.>
Thanks for everything.
<Cheers, Neale.>

Neale re: threadfins (Rainbows)    4/24/08 Hello again Neale, <Hello Aileen,> I have been fish keeping almost a year now and it amazes me how much I learn every time I look through pages of this site. Sometimes too much and the information gets all jumbled in my head (could be age too) and other times I learn enough to lead me to ask more questions.. it really is a wonder resource. <Thank you!> You mentioned some time ago that if I wanted threadfins I should consider another tank. I thought you were nuts at the time but...I am going to look at a used 40g tomorrow. Actually somebody had a 100g I can have but I think two monster tanks might be a bit much. My thinking is leading me to include in this tank: threadfin rainbows, wrestling halfbeaks, Corydoras and then I was wondering about bumblebee gobies or something with some colour. I was reading on WWM that most bumblebee gobies are considered brackish except one species, which may or may not, tolerate fresh water better? <BBGs are complicated: you cannot possibly identify species; even scientists have trouble doing this under a microscope, let alone with live fish! Most BBG species seem to be found in a variety of habitats, from blackwater streams to brackish water. But in aquaria they are temperamental, and slightly brackish water does seem optimal. This is a lot like Mollies for example, which may be freshwater fish in the wild, but unquestionably are easier to keep in brackish. Because BBGs are very difficult to keep well fed, I'd not keep them in a community tank.> My water is liquid rock. What are your thoughts on this community and any numbers you may think appropriate? Are there any other species you might include instead? <Almost anything that doesn't explicitly need soft water should thrive. pH stability is more important than pH value in most cases, and people routinely keep all sorts of things in hard water conditions. With Threadfin Rainbows, I'd be looking at Corydoras (and their relatives, like Aspidoras and Dianema) in terms of bottom dwellers. Kuhli loaches and small Loricariidae such as Whiptail Catfish would also be appropriate. You might also opt for some surface fish like Halfbeaks. Tetras and Barbs are best avoided because of potential problems with fin nipping, but Rasboras and other small Rainbowfish are certainly an option. Livebearers are certainly a possibility, though some Goodeidae are fin nippers so choose with care.> And since I have your attention, I was reading on here some time ago about separating swordfish fry before the appearance of the sword to prevent inbreeding. So I immediately set up another 10 gal to do so. But I realized when I was trying to sex them that they appear to be all female! Is this a probability? <No. While the idea that Swordtails change sex is widely held, there are actually no scientific studies that backs it up. It is much more probable that aquarists mistake undeveloped males for females. Male livebearers don't develop their sexual characteristics until a certain age (usually around 2-3 months depending on the species). Obviously until the gonopodium is formed they cannot fertilise the females, so you don't need to separate them until that time.> Or am I missing something like the triangular fin I am supposed to be seeing on only the females? Is the differentiation not as great in fry as adults? I ended up separating by size as it seemed the best alternative at the time. Since I was having so much trouble purchasing healthy vibrant red swords I decided to keep the try of a lone surviving, vibrant female. The batch was small but healthy, I have not lost any and they are about 5 months old. But still, not a sword in the bunch...I was hoping for some nice deep red males for another long term plan. <If you have just 5 fry, it is statistically possible, though unlikely, they are all one sex. But if the fry are less than a couple months old, you can't sex them anyway.> Thanks in advance for your help Aileen <Good luck, Neale.>

Rainbow-Killies-Planted Tank set Up  9/12/06 Hi, I'm in the process of planning a FW planted 54g corner tank (38"x27"x22") and was wondering if I could get a second opinion on a stocking list. Equipment will be an Eheim 2028 can. filter (275gph output), 300w in line heater, 55w pc light w/6700k bulb, 15g QT tank and a separate 15g hospital tank. I'm planning on weekly water changes of approx. 10 gallons, (more if nitrates rise beyond 20ppm.) Also, the water from my tap tests: 7.2 pH, 3 degrees KH and 6 degrees GH. My current stocking plan is: 1m & 3f threadfin rainbows, I. werneri 1m & 3f Pacific blue-eyes, P. signifier 1m & 3f forktail blue-eyes, P. furcatus 1m & 1f red-lined killifish, A. striatum 1m & 1f rainbow notho, n. rachovi 1m & 3f spotted blue-eyes, p. gertrudae 1m & 1f clown killifish, a. annulatus 1m & 1f blue notho, n. patrizi My main questions would be... Too many fish? < Between the filter and the plants you should be able to handle the nitrate load.> Any obvious aggression/territoriality problems sure to surface over the weeks?? < Many of the rainbows are in the same genus. I would expect males not to get along. The rainbows may be too active for the Killies and out compete them for food.> I'd rather have less fish than more problems. Also, should all of these guys be okay with my tap water? < Most of your fish would prefer a pH to be lower than 7, but you are very close already.> And any suggestion on a temperature that everyone would be happy with? Thanks in advance for your input and dedication to helping the hobby, (and hobbyist.) < Go with 77 F and thanks for your kind words.-Chuck> Enough already? Adding Melanotaeniids to a largely FW Amazon mix   1/31/07 Hi, <Hello> Thanks for running such a fantastic site.  It has been a real help with a whole bunch of questions that I have had.  However, I now have one that I am not sure how to work out the answer to. <We're in the same boat...> I'd really like to add a few Dwarf Neon Rainbows to my tank (Juwel Rekord 96l / 25g US).  Ideally 2 males and 4 females as I read that you need a 1:2 male female ratio. <Better than "even pairs" yes> The staff at more than one LFS have said that it would be fine, but I suspect that I am pretty much up against the carrying capacity of my set up. As it has been healthy (more or less) for the year or so since it was set up, I don't want to risk messing things up.  The current inhabitants are: 9 x Neon Tetra 5 X Oto 6 x Amano Shrimp 3 x Corydoras What do you think? <Mmm, there's room enough, but the Rainbows do "like" different water quality than the fishes you presently have... likely some "middling ground" could/can be found to suit all here though> Enough already, or should I go for the Rainbows?  I guess the alternative would be to wait until some of my fish die off through (hopefully) old age. Thanks in advance. Phil <Do take a read on... WWM, Fishbase.org re the water conditions of all these fish species. Bob Fenner>

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