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FAQs on the Livebearing Toothed Carps, Poeciliid Fishes Compatibility

Related Articles: Poeciliids: Guppies, Platies, Swordtails, Mollies by Neale Monks, Livebearing Fishes by Bob Fenner,

Related FAQs: Poeciliids 1, Poeciliids 2, Guppies, Platies, Swordtails, MolliesLivebearer Identification, Livebearer Behavior, Livebearer Selection, Livebearer Systems, Livebearer Feeding, Livebearer Disease, Livebearer Reproduction,

Keeping all males can work out...

Guppies      1/25/15
My male guppies are attack my male sunburst platy. Why are they doing this and how can i keep them for doing this. We added 4 female guppies to the tank today.
Thank you
<Male livebearers are aggressive towards each other, and pushy towards females. My guess here is that the male Platy has roughly the same bigger, more rounded body shape as a female Guppy, so the male Guppies aren't fighting him... they're trying to mate with him! Always add twice as many females as males to any livebearer aquarium if you want to keep both sexes. Otherwise don't mix them at all. Four males, four females is asking for trouble. Cheers, Neale.>

Retail fish store questions, treatment/s for livebearer losses     – 11/19/12
I recently found your site and it has been very helpful, so thanks!  I run a retail full line pet store and have had some years hobbyist experience (though we know how different that is!).  However, I have had some struggles with disease.
 <Most all of us do; in fact, there are no exceptions I'm aware of>
  We currently follow your acclimation procedures, but do not have the facilities to quarantine.  We have been feeding frozen food with Metronidazole and Sea Chem's focus as well as a few drops of liquid garlic every other day for the first week upon arrival.  This has done away with the Ich issue and helped with overall health.

  However, we still get issues with our live bearers and some bacterial problems.  I prefer not to add too much to the system for obvious reasons, would rather have things fed to them orally when possible.  Any suggestions are much appreciated!
<Mmm, well, you do what you can water-quality wise I take it... provide a good staple food (am a huge fan of the Spectrum line)... Do you have a system in-place for tracking losses, including the sources... where you buy from? This can really help in the long/er haul. Please see here Re:
Thank you!
<There are some pro-biotic items of worth... I really don't want to encourage you, the practice of continuously feeding Metronidazole (too toxic in constant use) or antibiotics (trouble to no use), even Anthelminthics... Bob Fenner>

Any compatibility issues in a 29 gallon between pearl Gouramis and smaller livebearers? 5/12/2011
Hi. I am setting up a new 29 gallon tank, and I am trying to decide what to stock it with. I really like Gouramis, and I'd like to put a pair of pearl Gouramis (Trichogaster leeri) into the tank. I am choosing them because the reading I've done suggests they are less aggressive than species like the blue Gourami (Trichogaster trichopterus) and more likely to work well in a community.
<In general, twixt these congeners, this is so>
I would also like to add the inhabitants of a smaller tank I have into the 29 gallon as well. I have four platies (the small two inch kind, not the larger wags) and one Ancistrus/Bristlenose catfish. Will there be any compatibility issues with the pearl Gouramis and these inhabitants?
<Should be fine together here, though I'd stock one male T. leeri w/ two females>
I'm primarily concerned with for the platies, as they are quite a bit smaller the pearl Gourami will be.
Lastly, I would like to get maybe three or four small balloon mollies to go in the tank (one male, the rest females). Will that be too much livestock for the tank (or might there be room for more fish)?
<Should be fine, though am not a fan of this sport mutation... and you'll need to be more careful re not letting the system water slip into acidic condition, nor nitrogenous waste accumulation w/ the mollies presence>
Are the balloon mollies, which are a little more aggressive than platies, likely to nip fins or cause other issues? Will the Gouramis bother them?
<Are all about the same mixable/aggressive. Again, I give you good odds of their mixing behaviorally>
Thanks in advance for your help!
<Welcome! Bob Fenner>

Aggressive Molly 2/23/08 Hi, I am fairly new to the hobby...I have in my tank one black male molly, one male Sailfin molly and four male guppy's in brackish water. The guppy's are new additions and the black molly seems to chase all of the guppy's constantly to the point were they just hide amongst plants. This is not new behavior it did the same with the other black molly I used to keep, to the point I am convinced it died from the stress/bullying...just my guess it may of been sick/weak but I'm sure it was bullying. I don't want the same thing to happen to My Guppy's is the only option to remove the problem fish? I don't have another tank so I would have to take it back to store. Would you recommend taking the black Molly out of the tank? <This behaviour is (unfortunately) all too common in home aquaria. There really isn't a fix. Male livebearers don't live long (their smaller size and brighter colours mean males are more vulnerable to predation than the females). So all they think about is monopolising access to the females as much as possible until they die! Mollies and Guppies both belong to the same genus, Poecilia, and view one another as potential rivals. Since the Guppy is so much smaller than the Molly, it is typically the Guppy that gets bullied and the Molly that does the bullying. It is universally good advice to keep livebearers as one species per tank and ideally one male per 3 or more females to avoid precisely these sorts of problem. Anything else is ALWAYS a gamble; either the males fight with each other the males harass the females, leading to miscarriages (and obviously fewer babies). Adding additional females may dilute the problem somewhat, but it never really fixes it. Cheers, Neale.> 

Livebearer tussle a thon   5/9/06 I have already received a response to the items below (just can't find the email right now) and thought I would include it as background for my current question... <Thanks> I'm looking for suggestions as to what to do with "Bubbles"...the skittish male platy in the 10g tank.  The female molly is fairly aggressive with him, especially at feeding time.  I try to put food at both ends of the tank, but when he tries to eat, she still chases and nips at him. If I put him back into the 35g, the other male platy chases and nips at him. If I put the female molly into the 35g, I'm sure the male molly will be after her again and they will start fighting again (he still hasn't completely healed from her last nips). The only things I can think of are 1) put the female molly in the 35g, but add 1 or 2 more female mollies at the same time?, <This will likely work> 2) then add a few female platies to the 10g for "Bubbles"? <Sounds very good> Any ideas would be greatly appreciated. <I would do what you state. Bob Fenner> (FYI...the 10g is my 3 yr. old son's aquarium.  He had 5 fish, now has 2 and keeps asking me where all of his fish are going!) Donna Guppies My sister had two guppies. One male the other female. One day she found her male guppy at the bottom of her bowl, dead. Would a female guppy be  aggressive enough to kill a male guppy? She also had baby guppies about 5 days after he died. Would this be part of the problem? And a week or two  later the female guppy ate all the babies. Is this normal? Sarah >> Sometimes a female will be very outgoing... but rarely kill a male guppy. Often these animals "just die" from "old age". At time of purchase, most only live about a year more. Having the babies didn't have anything to do with the males passing... but unless there is lots of space or decoration (plants, breeding "grass", or a breeding trap), livebearers, like guppies, platies, mollies and swordtails will definitely eat their young. Bob Fenner

Molly - Cory compatibility Doctor Fenner, <Call me Robare, just not late for din din> My wife and I recently started an aquarium in our apartment. While I was growing up, my grandfather was an avid fish keeper, and it really rubbed off onto me. Finally, I have a setup of my own, and we bought four beautiful black lyre tail mollies to start. <Ah, great> I've heard from several sources that Cory cats are good tank mates for mollies. However, I wanted to make sure before I head out to my local aquarium shop that Corys can handle the slightly harder water that mollies need. Thanks for your help! <Yes, good question... "modern" Corydoras catfishes are much more "plastic" (tolerant of wide, varying water conditions) than those of yore. Will do fine with Mollies, even tolerating a modicum of salt. Be chatting, Bob Fenner> -Chris

Those Crazy Mollies Dear Bob, Thank you so much for your website! Obviously much time and effort has gone into it, and it is outstanding! <Agreed! Anthony Calfo in for Bob while he is away> I have discovered 11 new baby mollies in my 39 gal brackish tank, it has only been set up for 3 weeks, and the 2 original mollies (male and female) were actually meant to be test fish, but surprise! What now? Do I have to remove babies from the tank? I only have one aquarium. <nope... mollies are one of the very least cannibalistic of livebearers... although no guarantees> Also, I really wanted some other kinds of fish in my tank, but what will not eat the babies? I was thinking of bumblebee goby (sp?)  <might work nicely is suitably brackish> and angel mono. <yikes! Too aggressive...grows too large and fast> Also, when will it be time to do the partial water change, and will it affect the babies?  <just do a normal and proper water change...same salinity/temperature in and out for aged/new water> Is there a possibility the babies will be different colors (other than white and gray like the parents)? <absolutely... much hybridization in livebearers> Thank you in advance for your help. Sue (ps I don't know if you need this info but my sp gravity is 1.008, temp is 75) <excellent Sue, keep learning and growing. Anthony>

Livebearing fish I Have a 20 gallon tank. I want a Mollie but I like them all. What should I do? <many livebearing fishes have similar requirements and are peaceful enough that they can be enjoyed in mixed company. Stable temperatures, slightly alkaline pH, and mildly brackish water and you have yourself a home in the 20 gallon for 12-15 assorted platies, mollies and swordtails. Resist putting too many aggressive males in the tank and be prepared for the inevitable reproduction that will occur. Have an outlet for the babies or specialize by species or gender instead. Best regards, Anthony>

Re: Guppy and Molly Fry together Hello, My silver Molly had babies (4 weeks ago), and they've been put in a fry net that hangs on the side of my 10 gallon tank.  My guppy gave birth to 17 fry 2 days ago.  Can I keep both the guppy and molly babies together in the same fry net?  My molly originally had 12 babies.  There's only 4 left.  Although they are bigger (4 weeks old) than the guppies. is keeping them together a good idea?  At this moment I have another 10 gallon goldfish tank.  So I don't really have another aquarium set up with a heater for the babies.  In my warm water aquarium, I have 3 guppies (1 female/2 males), 3 mollies (2 females/1 male), 3 neon tetras and 1 Siamese algae eater.   Thanks so much Kia Carnelus <Hi Kia, they would probably be ok in the same fry net, but if you want to be extra cautious you could get a second fry net. Best of luck -Gage>

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