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FAQs on the Molly Health/Disease: Diagnosis  

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

FAQs on Molly Disease: Molly Disease 1, Molly Disease 2, Molly Disease 3, Molly Disease 4, Molly Disease 5, Molly Health 6, Molly Health 7, Molly Health 8, Molly Health ,
FAQs on Molly Disease by Category: Nutritional (e.g. HLLE), Social, Infectious (Virus, Bacterial, Fungal), Parasitic (Ich, Velvet...), Genetic, Treatments
FAQs on Molly Reproduction/Breeding
Molly Reproduction 1, Molly Reproduction 2, Molly Reproduction 3,

Mollies. Again.       2/14/17
Hi, Neale - long time, no questions! Hope you had a good holiday and that the new year is treating you well.
<All good; thanks for asking.>
This morning we noticed that we have a silver sailfin Molly that's just lying on the bottom or swimming lethargically, using only her pectoral fins. She doesn't use her tail to swim at all. Her tailfin seems kind of shredded lengthwise, but doesn't look bitten. She had gotten big, we thought she was pregnant (assuming one of the 7 young mollies is a male), but she seems slimmer now. We have seen any fry in the tank, though we didn't really look (I'm only just now thinking of it).
We have another Molly, a creamsicle, that is starting to shimmy.
<Typically a stress reaction, though quite what the stress factor might be isn't always obvious. Mollies are easily stressed by chilling, nitrate, and the wrong water chemistry, though like all fish, non-zero ammonia and nitrite are issues too.>

The numbers are good in the tank - ammonia and nitrite are 0, nitrate is 20.
<Sounds good, but no mention of water chemistry here. Will (re-) state the importance of carbonate hardness to Mollies; alkaline water with a basic pH is an essential, especially if salt is not added to the water. Tanks will acidify between water changes, and this causes problems for Mollies in particular. Simply doing a substantial water change or three will often help Mollies return to their normal happy selves. Failing that, adjusting water chemistry slightly, by the addition of sodium bicarbonate -- one teaspoon per 40 litres/10 US gallons is a good start. Easiest approach here
is estimate size of tank, make up the correct solution for that volume, and then add to the tank in small amounts across a few days, giving time for the fish to adapt. Alternatively, just add the right amount of a given bucket of water (so might easily be a quarter teaspoon for a 2.5 gallon bucket) and do your water changes as per normal. I do prefer to keep Mollies in low-end brackish conditions, but understand that isn't an option in all cases. Read up on the pros/cons of this, and act accordingly. Would also check the heater, and maybe turn it up a notch, Mollies preferring quite balmy conditions compared with standard community tank fare; 28C/82F is not out of line for the bigger, sailfin varieties in particular.>
Tell me what I forgot to tell you and I'll provide the info, but this is about it, that I can see. As always, thanks so much for your help!
<Most welcome.>
Tom & Maria
<Cheers, Neale.>

re: Mollies. Again.     2/14/17
The water is relatively hard, and it goes in at around pH 7.8, then the tank adjusts up to 8.0 to 8.2 with the bubble stone and stays there. Maria changes the water weekly at a 25% change. The numbers have all been stable NH3/4, nitrate, nitrite, pH, etc, for months.
She's still hanging in there, but in a head up position. Could this be bacterial?
<Yes, but environment is what you look at first.
If you're content that the tank is good, then sure, treat with an antibiotic. Livebearers are sometimes given to strange "wasting" diseases after a certain length of time -- whether old age, dietary shortcomings (do bear in mind they're herbivores in the wild), social stress, or inbreeding is hard to say. But colonies of livebearers frequently do well for years, but individual fish may have substantially shorter lifespans than you might expect.>
Why would the tail separate into lengthwise strips?
<Typically physical damage, such as fighting. Do bear in mind Mollies are prone to fighting. You could medicate as per Finrot, but keep a close eye on the fish for evidence of squabbling. Cheers, Neale.>

Re: Hello and Thank You      1/24/17
Hello Neal,
Happy New Year.
<Likewise, Maria!>
one of my mollies has swollen, red gills on one side. the other side looks ok. I change water weekly: ammonium, nitrite are 0. nitrate has never been above 40ppm. what could cause this problem?
<Difficult to say. If just the one side, physical damage is certainly possible. Fighting, failed predatory attack; getting stuck on a filter inlet; clumsy handling by a human with a net can all damage the opercula and the gills underneath them. If the fish is otherwise healthy (in particular: a healthy weight, nice and active, and not showing signs of things like greyish mucous patches on the flanks) I'd tend to leave things be. But if alongside other maladies, might be worth using an antibiotic. Mollies can exhibit "wasting" symptoms that typically include fin clamping; rocking from side to side ("the Shimmies"); concave flanks as they lose weight; mucous/pale patches on their flanks; and a general appearance of
lethargy and disinterest.>
regards, Maria
<Cheers, Neale.>

Sick Molly's; no data, rdg.     10/7/15
I am not sure if I am in the right area but I need some help my water is 0.05
<.... is this specific gravity? If so; likely you mean 1.005. What salt/s did you use here?>
I have mollies with some weird symptoms started out like dry looking patches and now looks like this orange one she is the only one that looks like this they start out like the balloon Molly and progresses there are only 3 I can see that look like this but only the orange that looks this bad I found 2 baby's with what looks like little holes in there head and one baby his eye was white and pooped out I believe
<... need more data; re water quality, system, maintenance, feeding, history of the system. Let's have you read here:
and the linked files above.... for input, and to grant you an idea of what sorts of info. we're looking for. Bob Fenner>

Re: Sick Molly's    10/7/15

Sorry I am sick and not functioning on all cylinders myself it is specific gravity and it is 1.005
<Mmm; if you had other livestock.... than shown in your pix; I might well be raising the "saltiness" here>
I use marine salt by instant ocean
<Ah good>
tank is over a year old and cycled I use SeaChem stability and ammonia alert it's o it only measures free ammonia but I also checked with a ammonia tube tester it shows zero I use a biological cascade 1000. I do 15% water changes weekly. I test with high range ph test kit it is 7.5
Nitrite is 0 nitrate is 5.0
I have had issues with phosphates getting up between 1.0 and 2.0
<Meh; not to worry>
but use a phosphate remover, also by SeaChem. I only have 1 live moss ball in the tank it has really good oxygenation I have 1 Plato
<Pupil of Aristotle?>
1 shrimp a few zerite snails
<Zerite then>
it's a 45 gallon corner tank and 4 adult female mollies, 6 juveniles and honestly could not tell you how many babies my levels were fine so didn't worry about it I want to give them away but can't till I know what's up in this tank I got Molly's all at once never added any more snails were added after and shrimp feed omega one twice daily micro pellets for babies or crush the omega one in a pill crusher I do both I have city water, use aqua safe to remove chlorine my temp is 80.2. I have used Metronidazole in the water it was by apI twice
<Don't keep putting this in: Toxic>
48 hour intervals then I started giving mixed 1/8 tsp api to 1/2 tbs omega one soaked in 1/2 tbs water for 30 min now I have started using life guard
<For what? What for?>
while waiting to find out if anything can be done.
<...> really <...>
I have not seen anything like the pics I have sent you, do you have any idea what this could be I believe my mollies came with whirling disease I had the whirled for a year I euthanized her when she finally stopped eating I kept her in a floating baby nursery with a nylon bottom lost a lot of babies to this disease it finally stopped I hope.
Colleen ^>,<^
<.... wish I had a microscope nearby there.... Do you have another system you can move just the mollies to; jack up the salinity? BobF>

Re: Sick Molly's     10/8/15
I have them in a separate quarantine tank just has the 2 mollies a baby Molly that is twirling but has since stopped a baby with a white eye and 2 small babies with what looks like a tiny whole in there head nothing else in this 15 gallon quarantine tank
Colleen ^>,<^
<Do see my previous message, and Bob's; do also read:
Mollies aren't difficult to keep in (very) hard or (even slightly) brackish water, but are endlessly delicate if kept otherwise. Sensitive to crowding, nitrate, cold, and various other factors. Cheers, Neale.>

Re: Sick Molly's      10/9/15
Well I thought I read everything but got nothing I didn't already know my levels are fine in everything,
<Please don't tell me this. It's no use to me. What, specifically, did you measure? What numbers did you get?
Many hobbyists think their tank is "fine" but they're not. By "everything" do you include salinity? pH? Hardness? Nitrate?>
but I didn't read anything that you thought it might be or what to try I am old and have worked really hard to help them they came sick with clamped fins in fresh water of course, I have read a lot on that site you sent a long time ago, if you sent something that might help I must have missed, I think I am done, euthanize the lot 9 separate tanks because of all these
babies, but they all come initially from the same tank,
<Seems a bit extreme. Let's review. Mollies are most sensitive to environmental issues. Specifically, coldness (keep them at 25-28 C if possible); acidity (keep them at pH 7-8.5); and hardness, most easily dealt with by keeping them in brackish water, around a teaspoon of salt per litre (about 3-4 per US gallon) being about right. Farmed Mollies can suffer from
some "catchy" diseases, with Camallanus worms and "Slime Disease" (also known as Costia) being the two most difficult ones to medicate against. By contrast, while Fungus and Whitespot do occur, as does Velvet, all these are easily treated. But do remember to remove carbon from the filter before using medicines. Finally, using salt often helps moderate or even eliminate diseases.>
I feel I can't find new homes till I know what's going on. So it's time to euthanize unless I can come up with something else to try. Maybe I missed something I will go back and look but I just saw the one message and it was hard to follow.
Colleen ^>,<^
<Hmm... not sure this is difficult to read, and would start here:
Most fish health problems are environmental, especially where many fish are sick at the same time. Review conditions, or at least TELL ME the values on your test kit, and we can take it from there. Cheers, Neale.>

Re: Sick Molly's       10/10/15
I told you all the values when I started messaging you about the mollies I use specific gravity to test their saline,1.005 I have sent numerous messages in the past few days with pictures and gave you all the values in the tank, how I feed what I feed and there not all sick and only this fish looks like this and I felt was getting any info on meds or how to help so euthanized today
<May have sent this information before Colleen, but there are several of us who help out at WWM, and I don't recall reading a message with those values. Try to imagine what it's like for us. We get hundreds of messages a week, and simply can't keep track of every bit of information. So when someone says they sent a message to us last week with a piece of
information in it, that's a lot less helpful to us than resending that piece of information in a new email. Just the way it works, Colleen, I'm afraid. We're volunteers, we're offering a free service, and what we're trying to do is incredibly difficult. Imagine a doctor diagnosing a human illness by email. That's the situation here. If your fish tank was in front of us, and we could do all the test kits immediately, that'd be great. But we aren't with you, and we rely on you to do the tests. If you can't send test kit information to us, you're basically asking us to figure something out with 90% of the important information missing. I'm not exaggerating there. Water quality and water chemistry are the two main reasons fish sicken and die. All the other reasons are rare.>
These are some better close ups I am old and not feeling well so I just can't go through all the info again I am sure if you go back and read you will find what you need,
<Indeed you had, and with a bit of effort I've found them. pH 7.5; fine.
But no information on hardness. Let's assume it's adequate. Specific gravity 1.005 is excellent. Nitrite you say is zero, nitrate 5.0. This latter value is very low, which is good, but I'm normally skeptical of such low nitrate values. Why? Because most urban and suburban water supplies are well over 20 mg/l nitrate, often 40 mg/l. Certainly in England where I am!
But if you're out in the countryside somewhere and use well water or something with very low nitrate, then your test reading might be accurate.
Nonetheless, keep an open mind about this nitrate value. Test kits don't always measure accurately, or may be difficult to read.>
and to be honest you guys are who ever I have been messaging with have been snappy, the rolling eye comment because I told you I was using life guard," because I did not know what else to do while I was waiting for information"!!!!!! And you asked why I was treating with life guard, then did that eye comment thing.
<Hmm... I don't think these comments came from me. But in any case, we're sometimes snappy because we've got a lot of sick fish questions to get through, and it can be frustrating sometimes when we're dealing with willful ignorance -- not in your case, but does happen rather often, where people hang on to ideas (like Bettas can live in unheated bowls) because they
prefer ignorance (and fish dying, only to be replaced a week later) from accepting they're wrong (and spending more money). As folks who like pet fish and turtles, what we mostly help with here, we get a bit worn down by this at times, and it may become obvious if we're a little short at times.
Don't take it personally. If we were really mean people, we'd not be doing this for free, and we'd have just ignored you. Judge a man by his actions rather than his words, is what I'm saying.>
After I told you why I was using it. I am not a expert but do care about my fish, have worked very hard to help them I have purchased more and more tanks because of the crowding, I am just euthanizing any sick fish I see, I have tried for a year to get a straight answer and can't so I am done,
<Sometimes there just isn't a single straight answer. Mollies are plagued with problems in the US especially, kind of how Neons and Guppies are here in the UK. I guess breeding a fish to a price point rather than a quality has been the cause. But in any case, some problems are difficult to diagnose. Your fish may well have had more than one problem, and while I
suspect the blisters (which I hadn't seen clearly before) are from exposure to some sort of toxin, it's hard to say what. Blisters aren't normally caused by common disease organisms, or genetics, but tend to be environmental, sometimes mediated through a viral infection (such as Lymphocystis, which is untreatable but not normally fatal, and often clears
up after some months, even years). Even if you think the water is 100% perfect, it almost certainly wasn't. Copper perhaps, or something airborne like paint fumes might have been getting into the water. It's really hard to say. On the up side, since this isn't likely to be contagious or genetic, any healthy Mollies should remain healthy if their environment is good. Review, as previously discussed, and act accordingly. Think about what might have been getting into the water, and perhaps swap your current water conditioner for something that specifically neutralises copper, ammonia and heavy metals. Relocate the tank if it's somewhere near a source of fumes, and perhaps use carbon in the filter (not normally a fan) and see if that helps (will need replacing every couple of weeks though). Carbon has the useful trait of removing certain dissolved chemicals from the water that normal filtration does not.>
maybe you just did not get my e-mails and all the info and pics I sent you, thank you for your time have a nice Day.
<There's no single answer here, which I'm sure is frustrating. But much to think about. Cheers, Neale.>

Mollies dying; diag., trtmt.s f'      9/1/15
I apologize I hit send before checking my grammar and spelling, as I am messaging from my phone...I will correct...
<Not a problem.>
Dear WWM Crew,
I noticed you had another person named Jace email you back in March of 2011 with similar issue that has not been solved and was wondering if you have any more insight now that some time has passed... I had 2 white mollies, 2 black mollies, 1 orange balloon sailfin molly and 1 gold panda molly in a 20 gallon cycled tank (fish purchased approx. 1 month ago), frequent water changes done (25-40% per wk),with regular testing, 0 ammonia, 0 nitrites and 5 nitrates (no spikes during this recent time) the mollies came from brackish water so I have kept this environment for them.
<Can you tell me how much salt you're adding? Brackish water suitable for Mollies would be something like 5 gram/litre (0.65 oz/US gallon). That gets you a specific gravity of 1.002 at 25 C/77 F. You can use digital scales at home to work out how much you'd want to add per bucket. For a 3 gallon bucket for example, that'd be 3 x 0.65 = 1.95, close enough to 2, oz per bucket. Make sense? Once you've measured it out you can use teaspoons and see how many teaspoons there are in that quantity of salt. It's about 5 teaspoons per 1 oz of salt, more or less, so we're talking about 2 x 5 =10 teaspoons per 3 gallon bucket. With me so far? Mollies will actually do even better at higher salinities, and even doubling this amount of salt
could be worthwhile if your aquarium is just Mollies and plastic plants/ornaments (real plants and most other fish won't be so keen).>
Anyhow, first I noticed definite Ich symptoms - as the black mollies, orange molly and panda molly were COVERED in white dots like salt grains (couldn't quite see any on the white mollies). I raised the temp to 86 degrees to speed up life cycle and increased the salt in the water to 3tsp per gallon
<3 x 6 gram per US gallon... 18 gram/US gallon... 18 gram/3.8 litres... 4.7 gram/litre... yes, that should certainly kill of Whitespot and Velvet.>
when white spots disappeared to kill the ich the natural way (without meds)...
<Salt is a medication... in some situations far more harmful than, say, antibiotics.>
Now, before the white spots disappeared, 1 white molly's tail fin just disappeared (frayed down the body) and then back half of her body started to look fuzzy and she just kept spiraling around tank so I euthanized her.
The next day, the 2nd white molly's mouth was swollen open & just started crashing in to the gravel upside down, gills heaving and could not move so I euthanized her also.
<Not good.>
A few days later, the orange balloon molly's lips looked the same, she crashed and died just like the white molly! So, I assumed the Ich overtook the fish because this all occurred before the white spots fell off any of the fish and the other fish were COVERED in salt grains so it just made sense.
<Possibly, but I'd be wondering if Velvet or even Costia is the issue here.
Costia is the old name for Ichthyobodo, and you'll see both names in aquarium books, though Costia (or "Slime Disease") are more often seen on medications. In any event, like Whitespot we're talking about a microscopic protozoan that latches onto the skin of the fish and causes damage. Costia does seem to become more lethal more quickly than Whitespot or Velvet.
Commonest symptom is the appearance of off-white patches (rather than the discrete salt grains of Whitespot or icing sugar/golden sheen of Velvet).
It's more difficult to treat than Whitespot, though some medications will treat both. Brackish water works well against it though, as do 2-20 minute seawater dips (35 gram/litre). Mollies tolerate seawater dips extremely well, so this is a useful approach. I'm mentioning Costia here because it's a bit of plague among Mollies, notoriously obvious on Black Mollies because of their colour, often as greyish patches on the face and flanks.>
So after a couple days of raising the heat slowly, the white spots all disappeared and I started the salt treatment (to kill the free floating Ich), when all of the sudden (now this is when it gets exactly the same as the email you received in 2011 that I found on your site from Jace that had no resolution or real answer) the 2 black mollies started hanging around the filter intake and the heater near the surface (but not gasping), with their tails down as if their tails were paralyzed (drooping) and if they swam under the waterfall from the filter,
<This is the famous "Shimmies" when Mollies are stressed and unable to swim properly. It's called the Shimmies because initially the Mollies rock from side to side as they tread water, as if shimmying.>
they were forced into somersaults uncontrollably but then would buoy back up to the surface, tail down again. I also noticed their bowel movements were a long, clearish-white hair-like string (with intermittent white beads every so often).
<Interesting. Copious white faeces indicate excess mucous in the gut, which in turn often points towards parasitic infections, most notoriously, Hexamita.>
The next day, one black molly started crashing nose down into the gravel and could not swim or right itself (just as the white ones!) He stopped breathing and I noticed its anus was extremely white. Now the other black molly is still hanging near the surface with her tail down, obviously about to suffer the same fate! The only other one left is the gold panda molly and she seems fine! Again no parameters changed drastically ever during this time, and the only identifiable problem I saw was the Ich, but, as I said, it cleared up before these last 2 started crashing and they started displaying these unidentifiable symptoms that even your site said were strange (back in 2011)...so, I'm wondering if anyone has any ideas?
Any new knowledge on this? Could it be Ich AND something else?
<Easily. Whitespot/Ick is pretty much ubiquitous, but it's so easy to treat in its early stages it shouldn't ever be lethal. But it's also easy for fish to pick up other infections, and among livebearing fish, Camallanus worms, Hexamita infections, and something called Tetrahymena are all worth thinking about. Hexamita is treated by using Metronidazole, and is discussed elsewhere on WWM; use the Google search facility on the top of each page and you shouldn't have any trouble finding out about Metronidazole (often used alongside an antibiotic). Now, Tetrahymena is something less widely discussed. It is sometimes known as Guppy Disease.
Superficially similar to Whitespot in terms of symptoms but far more immediately lethal. To save me rewriting a bunch of stuff about this disease, let me direct you to a piece about this disease I wrote over at FishChannel:
The bottom line is that there are no effective cures, though a combination of anti-protozoan medication (Metronidazole for example) alongside elevated salinity (the higher, the better) may help.>
I forgot to mention all the fish were purchased together and introduced to the cycled tank at the same time (which I would never do again obviously!)
But I am very curious what this is and what to do now? I don't want to proceed ignorantly and subject any more fish to whatever this issue was!
Please help as I cannot bear to lose any more or have to euthanize; I am an avid animal lover and it's breaking my heart!!
Thank you!
<Hope this helps. Cheers, Neale.>
Re: Mollies dying        9/2/15

Thank you so much, I will look into all of this information!
<Glad to help and good luck. Neale.>

Mollies     8/28/15
Hi I am worry about my black Molly it has a white spot on its neck just before its fin i don't know if I should go and buy a small tank and put it in because the tank has the new babies in it by the way my tank is 65gal and the other one is 20gal thank you
<Mmm; just one spot.... I would not over-react; would NOT treat or move the fish. The water in this system is hard and alkaline I take it; these fish fed a good deal of green-based foods? Bob Fenner>

balloon molly with growth      5/17/15
I have a Dalmatian balloon molly with a growth behind its right fin.
<Ahh; see this in your pix...>
It looks like a solid mass, grayish green in color, consistently growing. I would say it has doubled in the past few weeks. Please see attached picture. I would appreciate any insight.
<Such growths are more and more common... tumorous; from various supposed causes... Narrowed genetic bottlenecking from so-much inbreeding, hybridising... perhaps water quality, nutritional input. Naught to do re treatments other than improving the environment and foods/feeding. Bob Fenner>

Re: balloon molly with growth        5/20/15
So basically she is going to die....and there isn't much I can do to help?
<Mmm; perhaps not die soon; but nothing that I'm aware of... other than experimental surgery, medicine use>
If I am understanding your last sentence correctly, you are saying there isn't much that can be done in regard to treatments for the condition.
However, I can monitor water quality and nutritional input....? Are there better fish foods than others?
<Yes; please see WWM re Molly feeding. BobF>

Poecilia velifera Parasite or Bac. Concern      8/30/14
Greetings Crew, I've recently purchased(2 weeks ago) a few Sailfin Mollies.
I have them in 40g breeder quarantine tank filtered by a small aquaponic grow bed(7 gal), homemade interior filter and air stone. One female has a large stomach with no gravid spotting and does have a very slight prolapse in rectum.
<Mmm; perhaps a bit of Epsom Salt>
This fish is mostly clear(in coloration) and I've noticed a black, some what blotchy pigment spreading under skin. It started behind gill plate, down toward stomach and slowly progressing backward. The fish seems healthy aside from conditions mentioned, feeding well, active, etc. No other fish are showing symptoms.
<What other fish/es (species) are present? The water is hard, alkaline... salt/s present?>
The other females have delivered fry except for this one. I'm considering treating for parasites and/or bacterial infect.
<Mmm; dangerous to just add medicines w/o knowing specifically what you're treating>
I have Metronidazole
<Toxic... just one dose. See WWM re>
on hand and was considering using it. I also have Furan and PraziPro. I do have access to Oxytetracycline, if need be. Which would you suggest, if any at all?
<Again; none w/o better knowledge of cause/etiology here>

My water supply is "hard"
<How hard?>
and I do add marine salt.
<Ah; good... IF your other life can/will tolerate it>
Do you think I could omit the salt without any negative consequences?
<Can't say w/o knowing more... the other life present mostly>
Thanks for the great site. Aloha Brandon
<Welcome. Bob Fenner>
Re: Poecilia velifera Parasite or Bac. Concern       8/31/14

Thanks for reply Bob. These fish are quarantining in a tank just containing 4 female and 2 males sailfin Mollies.
<Ahh, thank goodness>
Really haven't noticed aggression towards any fish. The fish in question seems to be the most dominant fish in tank. Soon to be added to a larger school of strictly Sailfins. My water hardness hovers around 75mg/liter, ph of 8.3.
<Ahh; about what ours is>
What would be the best way to ID an internal protozoan infestation on a living fish?
<Sampling... and microscopic examination. A bit of this is gone over... on WWM>
Thanks for the help. Have a great weekend. Aloha Brandon
<And you, BobF>

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