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FAQs on the Rainbowfishes Compatibility

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 Selection, Rainbow Systems, Rainbow Feeding, Rainbow Disease, Rainbow Reproduction,


Tank mates - Betta with turquoise rainbows?      12/20/14
I know you have "rules" about writing questions, but I didn't find them so hopefully I don't get in trouble!
<You're doing fine>
I have had a 90 gallon tank set up for 2.5 years. I have a nexx API filter that is set up under the tank, with two of the canisters on it (not sure of their size or how else to describe them). The filter has a relatively strong flow i think, and I have an aerator and two heaters. There are a few plastic plants and other decorations. The fish seem happy - bristle nose Pleco (4 years old) and 6 turquoise rainbows (most at 2.5 years old, a couple are older). I like the simple life in my tank. I keep meaning to get a few more adult turquoise rainbows, and I will sometime soon, ensuring equal amounts male and female if possible.
<Better to have a surplus of females>

My question is, could I safely add one Betta splendens? Will it be fine living with the school and the fast flowing water? I feel it could find space away from the flow in this large tank, just not sure if they explore all levels of the tank. I did read the Betta articles on the site, but tank mate info isn't clear.
<Mmm; not a good choice here on the basis of the size of the system... in concert w/ the Rainbows being very eager eaters, I fear that your Betta will go hungry. You could regularly net it, move it to a floating trap of sorts and feed it there... but...
I don't feel particularly inclined to add other fish. Thought about a few live bearers but I honestly just like the rainbows. Any other single fish (or group of 3 or so) that would be a good addition that are interesting or colorful? I prefer happy, safe fish not a stressed community.
Thank you very much
Ontario, Canada
<Do see the Rainbowfish Comp. FAQs for other ideas. There are better choices in the way of Anabantoids here.
Bob Fenner>
re: Tank mates - Betta with turquoise rainbows?      12/20/14

I appreciate it, thanks a bunch.
<Certainly welcome. BobF>

Turquoise or Lake Kutubu Rainbowfish behavior      4/23/14
I was at the LFS today and there were some beautiful Turquoise rainbow fish there. There were only two left. The guy who works there said that if I did not have the emperor tetras in the 75 gallon that they would go well with the two angels. Is it true that these rainbow fish are really aggressive?
<Male Rainbowfish can be very feisty, yes. Keep in mixed sex groups, partly for behaviour and partly for better colours; ideally 6 or more, though one male and two females can work well enough.>
The males are the beautiful ones and I read they love to dominate and will bully or kill anything in the tank if it can.
<That's overstating the case a bit, but males will try to throw their weight around with any other similar-looking fish, typically other Rainbows. Generally peaceful towards everything else.>
They look big enough to eat most tetras or swordtails and maybe aggressive enough to stress to death a couple of larger angels who are non-aggressive.
<Rainbows can make excellent Angel companions, but do bear in mind Lake Kubutu Rainbows need hard, alkaline water. They will eat bite-sized fish (anything up to, say, small male Guppies) but aren't predators beyond that.
Good with similar sized barbs, characins, etc.>
Thank you
<Most welcome, Neale.>

Threadfin rainbow fish compatibility       4/9/12
I have 7 Emperor tetras and two angelfish in a 75 gallon. I was wondering if some Threadfin rainbow fish would work out. It seems as though most rainbows are big fast fish. Are Threadfin rainbow fish slow moving? thank you
<Hi Judy. Threadfins are not especially delicate once settled (mortality is quite high the first few days, so acclimate them carefully and avoid big changes in water chemistry). But they are small fish with tiny mouths, and find it hard to compete with greedy fish. I'd tend to favour keeping them with fish or similar or smaller size, such as Ricefish, Dwarf Rasboras, Pencilfish or Ember Tetras, or else with fish that simply don't feed in the same way, like Corydoras. Emperors are pretty active fish and a bit pushy at feeding time. In a really big tank like yours you might be fine, spreading the food around the tank so everyone gets a chance. Downside to this is at least some food will get missed by the midwater fish, and if you don't have catfish in there, it'll end up stoking the nitrate level. The deal breaker though might be the Angels: these are opportunistic predators, and small Threadfins are definitely snack-sized for large (potentially 15 cm/6 inch) Angels. You might consider Dwarf Rainbowfish instead, or else something like the Boesemanni Rainbowfish, a classic Angelfish companion.
Cheers, Neale.>

Forktail rainbow fish, comp.        12/6/12
Hello WWM crew, I have asked for (and received) great help previously. I currently have 2 tanks, one of which is a 20 gal long, est 4 months ago. It currently houses 7 zebra danios, 1 fancy guppy, 1 ADF, 4 ghost shrimp, 4 cherry shrimp and  2 zebra Nerite snails. I only use WWM as a source and have drawn a blank. My parameters are as follows- ammonia-0, nitrite-0, nitrate-5, ph 7.6. Temp 78. I was in the LFS and saw forktail rainbow fish. I searched re WWM and was unable to find specifics for the fish I have seen, can you give me some details for this fish so I can find out if it is compatible with what I have? Thanks so much,
<Hmm… Do you mean Pseudomugil furcatus? This is the Forktail Blue-eye. It's a nice schooling fish. Very peaceful and basically hardy. Keep in large groups (at least 8 or 10, rather than 5 or 6). It's one prime requirement is hard, alkaline water: 12+ degrees dH, pH 7-8. Basic care much like any other small fish, but since it's a stream-dwelling species, you do need a decent current, ample oxygen and excellent water quality. It does well in planted tanks but won't do well in overstocked systems with sluggish water flow. Other Pseudomugil are occasionally traded, notably Pseudomugil signifer and Pseudomugil gertrudae. The only other fish that you might have seen is the Threadfin Rainbowfish, Iriatherina werneri. Another superb aquarium species. Small, a bit delicate when initially purchased and moved to new water conditions, but once settled adaptable and hardy. Lots of colour forms occur in nature, but they're all charming fish, especially the males. I keep a school in a densely planted community tank alongside a Dwarf Gourami and a couple of small catfish. No problems at all, though they have tiny mouths so you need to really powder the flake up for them. Cheers, Neale.>
Re: Forktail rainbow fish     12/6/12

Hi Neale, Thanks for the quick and informative response. Am still not sure which fish it is, when I go back to the LFS I will try to find out the scientific name. I can say they were very small, I wasn't sure if this was because they were juveniles or not but I did not see any larger ones. They are also expensive (9$ per fish) so I want to be sure before I spend that
much on them. My tank is heavily planted and has a good current and is well oxygenated. Do you think that with the current inhabitants I would be overstocking with a school that size?
<In terms of stocking you should be fine. But Zebra Danios can be real bullies, even towards things like White Cloud Mountain Minnows. So I'd be leery of combining with Pseudomugil or Iriatherina spp.>
They are small but I don't want to risk it if it's not wise. Thanks Neale,
I really appreciate your time, Marya.
<Glad to help. Cheers, Neale.>

Platies and Dwarf Neon Rainbows, comp., stkg.     5/17/11
<Hey Jude/y>
I was wondering if Platies and Dwarf Neon Rainbows are compatible?
<Mmm, yes>
I have two male platies in a 29 gallon. Is this tank two small for the two and a couple of rainbows? Thank You!!!
<It is not... but I would get more than a couple of each... 3, 5... Bob Fenner>

Aggressive Boesemanni Rainbow Fish  8/15/10
Dear Crew,
I have recently discovered that one of my male Boesemanni Rainbows is a terror! He is kept in a 55 gallon aquarium with 3 fully grown angelfish, 2 neon tetras, and 7 other Boesemanni, which include 2 males and 5 females.
He constantly terrorizes the other rainbows, both females and males, but the males more so. He chases them into corners and won't let them come out. He is the biggest male rainbowfish and the best colored too, and I got him before the other 2 males (before there were just 3 females and him, but when I noticed some missing scales on the females, I stocked up some more to diffuse the aggression). I have separated him into the 10 gallon quarantine tank,
but I was wondering if I should return him to the LFS for a less aggressive one, or isolate him for a couple of weeks and then put him back (and hopefully his behavior will have changed by then!).
<I would try the latter... this isolation often serves to calm down such aggressors>
<Welcome. Bob Fenner>

Compatibility: Bolivian Ram and Rainbowfish  10/12/09
We are commencing to re-stock a 30 gallon community aquarium. It's been stable with a few fancy goldfish for a couple of years, but we are wanting to convert this aquarium to a tropical community. All residents of this tank have now been moved to new homes.
<Very good.>
We are in the habit of regular water changes. We live in the Seattle area of Washington, USA. Our water tends towards softness, I believe.
<Soft can be good for South American and Southeast Asian fish in particular, but you do want a steady pH. A little information here in terms of water chemistry would be useful. But assuming something like pH 6.5-7.5, 5-15 degrees dH, then most community tropicals should do fine, with the obvious exceptions of livebearers, which prefer hard water.>
We have identified Bolivian Rams and Rainbowfish (Red, turquoise, emerald, etc.) as 2 types of fish that we'd definitely like to keep in this
<Rainbows are schooling fish, so keep at least six per species, and preferably equal numbers of males and females to ensure optimal colouration (if you don't have equal numbers of males and females, the males have no reason to colour up properly!). You usually can't sex most Melanotaenia species when young, but some foolish aquarists keeping Glossolepis incisus try to keep just males, and wonder why their fish don't look happy. In any even, a 30-gallon tank will be too small for most Rainbows, the only exceptions commonly traded would be Melanotaenia praecox (the Dwarf Rainbow) and perhaps the Telmatherina ladigesi (Celebes Rainbowfish). This latter species needs neutral, moderately hard water and doesn't like pH levels below 7, so it might not even be an option.>
Are these compatible in the same community?
<Yes. Most Rainbows like neutral, moderately hard water that isn't too warm, and this is optimal for Bolivian Rams, Mikrogeophagus altispinosus.>
If so, what conditions (temperature, PH, etc.) would be best for them?
<7.0-7.5, 10 degrees dH; 24-26 degrees C.>
Also, how many of each of these should we limit ourselves to?
<A pair of Mikrogeophagus altispinosus plus 6-8 Melanotaenia praecox would work fine in a decent length 30 gallon tank (i.e., not some daft hexagon or something, but a long, shallow rectangular tank).>
Can you please recommend other compatible tankmates for this community?
<Wouldn't add anything more to begin with. Possibly some Cherry Shrimps and Nerite Snails as scavengers/algae-eaters, but that's about it. Catfish tend to be harassed in small tanks when kept with Dwarf Cichlids. So while you could certainly add a school of Corydoras aeneus or similar if this was a 55-gallon tank or even perhaps a 40-gallon tank, a 30-gallon system is just too risky. Dwarf cichlids chase the catfish, nip them, even blind them. Not nice. If the tank was properly maintained for six months and there was enough light to get some green algae growing, a school of Otocinclus might be an option, but they're such sensitive fish I'd not recommend them.
Shrimps and Nerite snails are safer, much more effective algae-eaters.>
Thank you,
<Cheers, Neale.>

Re: Bolivian Ram and Rainbowfish 10/13/09
Thank you very much for your prompt and highly informative response to my previous questions.
<Most welcome.>
According to the test run at our local aquarium shop, our water has a pH of 7.1 and hardness of 2 degrees dH. Will this be a problem for Bolivian Rams and Rainbowfish?
<Yes. Water this soft, assuming it has a comparatively low carbonate hardness as well, less than 3 degrees KH, tends to be unstable. Do test the carbonate hardness, because this really is critical. Read here:
I don't recommend relying on shops to do your water tests, by the way. It's a good habit to get a few basic test kits of your own, so you can keep track of water chemistry and water quality.>
Is there anything we need to do to condition our water?
<Quite possibly. If your water has low general hardness (measured in degrees dH) and low carbonate hardness (measured in degrees KH), it will likely be too soft to keep these fish comfortably. One approach is to add limited amounts of Rift Valley Cichlid Salt mix, as described here:
You wouldn't use the full dose, but around a quarter to a half the dose.
Let's say you started with a quarter dose, that'd be 1 teaspoon baking soda, 1 tablespoon Epsom salt, and 1 teaspoon marine salt mix per 20 US gallons.>
Our tank is the long, rectangular 30 gallon variety. We like your suggestion of a pair of Bolivian Rams and 3 pair of Neon Dwarf Rainbows to begin with. Can we add more fish than this eventually?
If so, would you suggest more Rams or more of the Dwarf Rainbows, or could we add another variety of fish?
<I'd not add more Rams, or they're likely to fight. Certainly, not more males anyway! As for Dwarf Rainbows, yes, a few more is always a plus. The bigger the group, the prettier they look, because they school nicely and show better colours (they're happier!). You might add some Silver Hatchetfish, Pearl Danios or Halfbeaks at the top of the tank.
Alternatively, you could add a retiring catfish like a Bristlenose Plec, but the problem here might be if your cichlids spawn. The catfish would likely be harassed if it didn't have a suitable cave, and conversely, it would eat any eggs.>
Our next questions regard diet and habitat. Are there any special dietary and feeding requirements for either of these 2 species?
<A mix. You can't go far wrong with this: A good quality staple flake or pellet, regular offerings of wet-frozen bloodworms, and occasional treats of things like live daphnia and live brine shrimp.>
For instance, I read somewhere that Rainbows should have some fresh greens such as duckweed occasionally.
<No, not necessary. For one thing, duckweed can easily become a pest.
Rainbows feed primarily on insects that fall onto the surface of the water, as well as zooplankton and small crustaceans.>
Also, I understand that in the wild, most of their diet is live food, so do we need to supplement their flakes with something else?
<I don't recommend you use flake exclusively, if for no other reason than fish get bored with it. All dried foods, whether flakes, pellets, or freeze-dried foods, are also more likely to cause constipation (imagine what would happen if humans just ate beef jerky all the time...).
Wet-frozen foods tend to have a high "ash" content, and this works like fibre.>
And speaking of flakes, I understand that rainbows are surface feeders, so flakes or something that does not sink immediately is best. Is that true?
<They certainly don't want foods that sink right down to the bottom. But they will take food from the surface and from midwater equally happily. If all else fails, ask the retailer to feed the fish in front of you. Whatever they're eating, buy some of that!>
On the other hand, I read that the Bolivian Rams need to be fed a special Cichlid formula. Is this the case?
<Cichlids certainly need a varied diet otherwise become prone to various health issues including Hexamita, Hole-in-the-head, constipation, bloating, and perhaps other things too. Wild Bolivian Rams are substrate sifters -- their Latin name Mikrogeophagus means "little earth eater" -- so what they would do in the wild is take mouthfuls of sand, sift it across their gill rakers, and extract small invertebrates, algae, and bits of organic detritus. In captivity they happily do this, and it's charming to watch. I tend to give my cichlids wet-frozen rather than flake foods, and enjoy watching them sift out the bloodworms or whatever from the sand. It's fun to see. Of course, you might only want to do this a couple times a week, in which case a good quality sinking pellet such as Tetra Min or Hikari Micro Pellet would be a good place to start.>
Will they come up and eat the flakes or do we need to feed some sort of sinking food to the Rams? If so, what do you suggest?
<They won't feed from the surface, no. But they may well eat uneaten flakes that float down to the bottom.>
Regarding habitat, we have 2 or 3 plastic plants and a small cave formed out of a few rocks. We read that the Rams don't like bright light and should have some shade. Will the single cave be enough for the 2 Rams or will they each need their own?
<At least a cave each, ideally more than one.>
Or should there be some sort of special style of plant (such as floating plants) that we need to provide?
<Start with some Java fern and/or Anubias on bogwood roots, and throw some in some Indian Fern and Amazon Frogbit for the floating plants. Easy plants to keep, no need for a substrate (so cheap to grow!), and these will, together, provide plenty of shade.>
Finally, (for now at least) are there any other considerations that we should be made aware of regarding our setup?
<Consider using a thin layer of _smooth_ silica sand (from the garden centre, very cheap) about 1-2 cm deep for the bottom. You'll love watching your cichlids behave naturally, and they'll keep the sand nicely sifted and clean as a bonus. Much prettier than gravel, too.>
Thanks, Jeff
<Cheers, Neale.>

Rainbow / Gourami question... comp.    6/29/09
I have a 30 gallon tank of 6 Rainbow and 1 Gold Gourami (Trichogaster trichopterus). They seem to get along okay, but I am worried the Gourami may get aggressive as it gets bigger. Do you think this combination will work?
<It's only the male Trichogaster trichopterus that become aggressive, and even then, it's usually towards other gouramis, or at worst, other fish of similar general shape, such as cichlids. Males have longer dorsal fins than the females, so it's quite easy to tell them apart when you have a bunch of them in front of you, but if you have just one specimen, you may want to look at some photos in aquarium books to see whether yours is a boy or a girl. In any case, I'd fully expect your combination of Rainbowfish and a Gourami to work very well. Cheers, Neale.>

FW shark w/ Australian rainbowfish?  7/29/08 Hello, <Ave,> I currently have a red-finned shark (rainbow shark?) and a few angelicus Botia in a 30 gal. I was thinking about getting a few Australian rainbowfish (Melanotaenia australis), but I'm told my shark may get quite aggressive when he grows larger. <Correct; Epalzeorhynchos frenatum is indeed an aggressive and territorial species.> Would the shark and the rainbows work out, or would the rainbowfish get picked on? <They can coexist, but in a large tank where the Melanotaenia have space to avoid trouble. Not sure a 30 gallon tank is adequate for this though.> I figured since they'll top out at around the same size and the rainbowfish are quick swimmers that maybe they'd be alright? <Speed is the key, but that demands space if its to work. The Melanotaenia can't swim away from trouble if they have nowhere to swim to!> Also, could you recommend a schooling fish small enough to not take up too much space, but robust enough to survive the shark? <Do read here: http://www.wetwebmedia.com/FWSubWebIndex/redfinsharks.htm > I like little fish like harlequin Rasboras and neon tetras but I'm afraid they'd just get gobbled. <They won't be eaten by the Shark, but they will be harassed.> Thanks, Jessi <Cheers, Neale.>

Rainbows in a "peaceful" African tank  4/26/08 I have 90 gallon tall tank that is stocked with Peacocks and Haps (Total about 20, all juveniles ) . I still have top level of the water empty. Can i get 4-5 Rainbows Boesemanni? Do you have any experiences/recommendations? I know they are not same biotype but I heard Rainbows are tolerant to high PH . <Can be done, but not 100% reliable. Rainbowfish should be fine with non-aggressive cichlids of similar size, particularly if the cichlids are juveniles when introduced. But do keep a close eye on things, and we aware that some bullying, and even fatalities, can occur.> Or do you have a other fish suggestion for the top level for African tank. <Rainbows and livebearers are the usual recommendations. Depending on the Rift Valley cichlids being kept, options include things like Ameca splendens, Xenotoca eiseni, and swordtails. Choose fast, robust species with a certain degree of aggression themselves. Very occasionally you see Tanganyikan killifish (Lamprichthys tanganicus) on sale here in England, as well of course Cyprichromis spp. cichlids which are the classic open water cichlids.> I wanted to also thank you all for a great service that you do for this hobby. <You're welcome! Cheers, Neale.>

Extreme Delay, Sabrina's A Ditz - 08/26/2006 Rainbowfish comp. Hi WWM Crew, <Hi, Erin!> First, I would like to extend my most sincere thanks for the service you are providing to all of us interested in aquarium hobby. I have learned more in the past 2 months since finding your site than in the past 5 years I have had my 20 gallon. <Well....  with the considerable delay that's coming with this reply, I hope you don't hate me/us.  Yikes.  I really, REALLY need to move and shorten my commute time....> I also have a 55 gallon fresh water tank. The tank is moderately planted. The tank has one large and one small piece of drift wood and some large river rocks for structure.  I figure the actual volume of water at about 45-47 gallons.  It has been running for about 4 months now. I have introduced 6 Zebra Danios, 5 Cherry Shrimp, 2 Bristle Nose Catfish, and 2 Green Cory Cats. We are interested in creating a colorful and active community tank. After a lot of reading and a tour of 6 area fish stores I have developed an interest in Rainbow fish.  I realize there are many types of this general category of fish. I would prefer to have smaller fish with plenty of room so we have decide we would be most interested in the smaller varieties growing to a maximum length of about 3.5 inches.  One of the most appealing varieties is the Threadfin Rainbow (aka Iriatherina werneri).  I have some concerns regarding compatibility with our cherry shrimp.  I have read these fish are omnivores and that they have large mouths but their throats are narrow. As a result, special care must be taken to provide small enough pieces when feeding. I am still concerned they may have compatibility issues with my Cherry Shrimp. Do you think the Threadfins would eat them? <I rather doubt it, but I suppose it's possible.  Threadfins are really quite small, as Rainbowfish go.  I think I'd risk it. I do not want to unleash terror on the shrimp as they are my favorite tank inhabitants.  Also, do you think other types of Rainbows would be okay if the are of similar size or smaller?   <Probably.> I would also be interested in any general comment / reservations you may have about keeping this type of fish. Thanks for you time.   <I've never kept them myself.  I've heard that they are delicate and prone to Mycobacteriosis/"Fish TB"/"Rainbowfish Disease", so I would heartily recommend a longer-than-usual quarantine prior to adding them to your system, both to allow any symptoms of disease to show up and also to allow the fish a longer time to adjust to your water and care.> Erin Costenbader <All the best to you,  -Sabrina>

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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