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FAQs on the Molly Social Disease:

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

Related FAQs: Mollies 1, Mollies 2, Molly Identification FAQs, Molly Behavior FAQs, Molly Compatibility FAQs, Molly Selection FAQs, Molly System FAQs,
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: Environmental, Nutritional (e.g. HLLE), Infectious (Virus, Bacterial, Fungal), Parasitic (Ich, Velvet...), Genetic, Treatments
FAQs on Molly Reproduction/Breeding
Molly Reproduction 1, Molly Reproduction 2, Molly Reproduction 3,

All life must at least tolerate water quality conditions PLUS be compatible behavior-wise.

NOT so-called Chinese algae eaters... NOT Tetras or other soft, acidic water life, NOT cold water life with tropicals, NOR many catfish species.

Need to be placed more females than males...

Male molly seems 'lonely'     1/21/14
Hi crew,
I have a community tank with various fish but mainly mollies and platies.
Our largest female gave birth but died after a month. The male seemed to be pining for her, he kept low in the tank, started losing his colour and hid underneath the filter.
<Do read, here:
Almost certainly your "unhappy" Molly is responding to some other stress factor, perhaps environmental if water quality isn't spot-on (nitrate levels need to be below 20 mg/l in freshwater) or the water isn't hard enough (the harder the better, 15+ degrees dH hardness, pH 7.5-8.5).>
This morning he was just lying on the bottom of the tank and eventually died. Could this be a disease in our tank or does this happen with males that have mated with a female for a long time? (We have had them together for more than a year and they used to swim together all the time)
<Mollies do not need company, and form no bonds whatsoever with each other.
Male Mollies are aggressive towards one another, and will attempt to mate with any/all females that pass close to them.
They can be very persistent, and this can/does stress unreceptive (i.e., pregnant) females, potentially causing miscarriages and even the death of the female. Mollies are best kept in large groups with females outnumbering males by at least two to one; failing that, just keep virgin females.>
Thank you for your help,
<Most welcome, Neale.>

My Dalmatian Molly; sys., hlth.       1/1/14
I got a 36gallon tank for Christmas. I filled it with filtered water
<What do you mean by "filtered water"? Did you buy drinking water from a grocery store? Do you know the hardness and pH of this water? Do understand that tap water, if treated with water conditioner, is best for most tropical fish because it is inexpensive and you can afford to do large, frequent water changes (25% a week is a good target). While drinking water might sound a better idea, it's expensive, and "good" water that isn't changed very often won't help the fish in the long term. One last issue is water chemistry. Mollies (and Guppies, and indeed most other livebearers) need hard, alkaline water. If you keep them in soft water, they'll quickly sicken and die. If all else fails, add salt to the water. A good target here is 3-6 grams per litre (about 0.4-0.8 oz per US gallon, roughly 2-4 teaspoons per US gallon). Marine aquarium salt is ideal and inexpensive in the quantities required -- you'll find even a small box will last many months.>
and let it sit for 2-3 days with the filter and heater running and ever since it has remained at 76 degrees.
<Do understand that running the filter without fish in the tank does nothing to mature the aquarium. It's a good idea in the sense it shows you the aquarium is set up properly and isn't leaking, but other than that, it's pointless. The filter won't mature until you add fish. Unfortunately for you, Mollies are extremely bad fish for maturing new freshwater aquaria. Oddly enough they are very hardy in brackish and marine aquaria, and historically were often used to mature such tanks. But in plain freshwater tanks they very, very quickly sicken when exposed to non-zero ammonia and nitrite levels.>
Saturday I bought 3 fish. A blue guppy a yellow guppy and a Dalmatian lyre tail Molly. I don't want any babies so I got all males.
<Do understand these will fight. Mollies are not sociable, and males especially so.
Females are a better bet for a quiet aquarium, and even if they are pregnant, they'll eventually run out of babies and your tank will become a baby-free zone. Remove unwanted fry as necessary, and your local pet shop will probably take them. If you leave them in the tank, they're actually a good insurance policy for the future, bearing in mind not all your original fish might survive, and over the years, having younger fish to replace older ones is useful and economical.>
And they said add only 2-3 fish at a time.
<Yes. But Mollies are such bad fish for maturing tanks, even this won't guarantee success. Do note that adding salt as instructed above will turn the aquarium slightly brackish, dramatically increasing your odds of success (in brief, salt slightly detoxifies nitrite, and the hardness in marine aquarium mix further helps Mollies maintain better health.>
Well when I got them home I let the bag sit in the tank for a little bit before I put the fish in. Once I did so they seemed happy. Well a little while later I noticed the Molly was breathing really hard and I figured he was stressed.
<Correct observation. Did you do an ammonia or nitrite test? When you cycle an aquarium, first ammonia goes up and then comes down to zero within a couple weeks. A few days after the ammonia goes up, nitrite starts to go up as well. Eventually it comes down, usually within 3-4 weeks, by which time the aquarium is now cycled.>
He hasn't died yet but this morning I found my yellow guppy kept swimming to the top.
<Likewise, modern fancy Guppies are extremely sensitive delicate fish.>
He looked like he was trying to get some air then he would stop moving, turn upside down and sink to the bottom.
<Classic stress behaviour.>
He kept doing this and I noticed even when he was swimming back to the top his gills weren't moving they were just like sticking out. I took advantage that he kept swimming to the top and caught him in a bag. I let some water flow into the bag along with him and after about 15 minutes he wasn't "coming back to life" anymore and trying to get air. He was the calmest of them all and the most active I'm not sure what went wrong.
<Easy: you added sensitive fish to a non-cycled aquarium. While some fish are tough enough to go through this, with care on your part, Mollies and Guppies are not (at least, not in freshwater conditions).>
Now onto the story about the Molly... He really isn't social at all and sometimes his tail end (is that posterior end?) would be bent sideways and he would tread water like that for a minute or a couple minutes.
<This behaviour is called "Shimmying" and it's a neurological symptom often seen with Mollies and Guppies when stressed. It fixes itself if conditions improve.>
I don't know what to do
<Get a nitrite test kit (not a nitrate test kit, they're different). Do a test. If nitrite isn't zero, don't feed the fish, and do a 20-30% water changes (ideally, adding salt to each batch of new water as mentioned above). Regardless, do water changes every day for the first couple weeks.
Thereafter you might get away with changes every 2-3 days depending on the nitrite level. Expect all this hassle for the first 3-4 weeks until nitrite stays resolutely at zero for 2 or 3 days in succession. During this first 3-4 weeks from the time you add the first fish, feed extremely sparingly, a tiny amount (a 2-3 mm crumb per fish, say) and only every 2-3 days. Don't worry about fish starving. Isn't going to happen. Takes weeks! But ammonia and nitrite can kill fish within a day. Use your nitrite test kit regularly, every day or two.>
I don't know if something is wrong or what but I don't want it to die.
I don't notice him eating very much either.
<See above; not a problem. Will eat when conditions improve.>
I haven't had fish for several years but I thought I'd give it another shot. I'm extremely novice, I've never had more than a 5 gallon sponge bob square pants tank with a Betta in it until now.
<Hope this helps, Brooke. Do read:
Follow especially the links on that second article re: Molly disease; almost always caused by the environment, and what applies to Mollies largely applies to Guppies too. Cheers, Neale.>

shy Gourami and vertical molly 8/22/10
I have a 72 gallon fresh water community tank. Tank is fully cycled and established. Regular weekly maintenance (water change, gravel siphon, glass cleaned with cleaning tool and all water conditions monitored and within acceptable parameters.
<Meaning what, precisely? Mollies require very different water conditions to South American tetras, and it's hard to see how you can have "acceptable" water for both in one aquarium. Even if you don't maintain Mollies in brackish water -- and to be fair, some people manage to keep them in freshwater just fine -- they still need warm, hard, basic water.
Danios require cooler water, and Tetras softer water.>
No live plants, though several fake plants and multiple hiding spots for the varied fish There are 3 gouramis in the tanks (along with other species - all community/peaceful -Danios/tetras/mollies/2 clown loaches/Cory/Pleco).
<See above.>
Of the 3 gouramis, one is acting what I define as strange. During the "daytime' or when daytime light is on the tank, it will "hide" in one corner of the tank. However if I run the "blue" light that I have for night time viewing, this Gourami becomes active and swims throughout the whole tank and socializes with the other fish. During the day or with day lights on this
Gourami will run from the other gouramis as if being chased, however under the blue lights shows no such sign of submission and chases the others as much as anything else. No obvious physical issues, and seems to be eating regular.
<I do think this is aggression. Assuming this is Trichogaster trichopterus,
the males -- which have longer dorsal fins -- are famously aggressive towards one another. Adding more females might dilute things, and keeping just two males within a group of three is bound to cause problems because one male can always bully the other. Try keeping at least equal number of females to males, and either one male or at least three.>
Have also noticed that a silver molly (relatively new tank member - 2 weeks) swims around in a "vertical" posture, nose up/tail down - almost like a rocket ship taking off.
<This is likely "the Shimmies", a neurological issue related to poor environmental conditions. Mollies need 15+ degrees dH, pH 7.5-8.5, and a temperature between 25-30 degrees C. Danios won't enjoy water that warm, and neither will Corydoras or tetras such as Neons; all of these are better kept at 22-24 C. Obviously, most freshwater fish won't tolerate brackish water, but even the hard water Mollies need will significantly shorten the life of the more sensitive South American tetras such as Neons and Cardinals.>
It is capable of swimming horizontally, and will do so for a while and then go vertical even though it is swimming along a horizontal plane. My local fish supplier says that this is a common trait of this species, but I have never seen so before. Again no obvious physical or eating issues. Any thoughts/advice would be appreciated.
<It's possible the Molly has constipation or is simply genetically deformed, especially if the thing is inbred or one of those ghastly Balloon Mollies. But if the fins are clamped, or the fish rocks when treading water, then Shimmies is very likely the problem. Constipation can be cured using high-fibre foods such as peas and spinach, together with Epsom salt if needs be:
Genetic problems aren't fixable, and the Shimmies goes away usually if the Molly is given good conditions:
<Cheers, Neale.>
Re: shy Gourami and vertical molly
Thank you for your response,
<Glad to help.>
I will try provide the further information you require.
Maintenance: weekly water changes, approx 30%-40%, use floating glass cleaner to clean glass and gravel syphon to suction gravel. Fluval 404 canister filter Water conditions: Ph maintained at 7.0 as much as possible, checked twice a
week. Nitrates checked weekly usually around 5 (lowest number on scale).
Ammonia tested weekly usually 0-0.25 (keep a hang in tank monitor in the tank to visually check daily - unsure how accurate these are).
<Very inaccurate. Do have the water tested with a liquid test kit; if not zero, then you have a problem with water quality.>
Also check Phosphates and usually 0-0.25. Haven't tested the water hardness in a while, but believe it to be hard (will get test kit to test). Usually test water 2-3 days after water change to give numbers a chance to balance.
Is this the proper type schedule. Anything specific I should be checking as well?
<What you're doing sounds fine.>
Sorry not sure what you refer to as "basic" water?
<Basic is the opposite of acidic; i.e., pH 7 upwards. At school you might have learned "alkaline" for this, but actually alkaline means something quite specific, though closely related.>
Usually attempt to maintain a water temp of 76F (24C)
Food: TetraAlgae vegetable enhanced chips. Nutrafin Max sinking pellets (for bottom feeders (loaches) bloodworms (every 10 days or so as a treat
<All sounds fine.>
Tank inhabitants:
1 Bristlenose Pleco (2yrs in tank )
2 Clown loaches (2 years in tank)
6 Zebra Danios (3 months to 1.5 years)
6 Cardinal Tetras (1 year)
1 Juli Cory (1.5 years old)
2 black and 2 silver mollies (1 silver molly 1 year, other 3 - 2 weeks in tank). They are not balloon mollies.
3 Gouramis (1 moonlight and 2 sunburst - the moonlight Gourami is no problem (except chases the air bubbles), the solitary Gourami is one of the sunburst).
<Right, the Sunburst Gourami is, I believe, a variety of Colisa lalia, a very risky species. Highly prone to Mycobacteria infections as well as a viral infection all its own called Dwarf Gourami Iridovirus. Not a species I ever recommend. Sad, because it's a nice fish. But inbreeding and intensive farming has completely ruined this species.>
Between my LFS and the web, I thought I had done my homework regarding water/environment compatibility within the tank (www.peteducation.com/article.cfm?c=16+1911+1957&aid=2572
- was one article that led me to believe mollies and gouramis were compatible) - though I am sure there are others to indicate non-compatibility. However your information indicates the mollies do not fit within this grouping and I am willing to accept your analysis.
<It's not that you can't keep Mollies with Gouramis; it's that you can't *always* keep Mollies with Gouramis. About 50% of the time Mollies just don't do well in freshwater communities. Some folks write that off, and say if the Mollies aren't happy, take them out and try something else. Or alternatively, keep medicating as often as required. Or worse, treat them
as disposable fish, and when they're sick, euthanise them and buy some more. My argument is towards providing such conditions for Mollies that you have as near to 100% chance of success as possible. So certainly that means the water should be hard and basic (alkaline) but it also means keeping your options open so you can add some marine salt mix. Some tropical fish don't mind a little marine salt mix, and will thrive under those conditions. Most other livebearers for example, as well as things like Australian Rainbowfish, many Killifish and Cichlids, and certain catfish such as Brown Hoplos. But on the other hand, there are fish that dislike salt immensely, including most tetras, barbs and gouramis.>
You seem to indicate that the best move is to remove the mollies from the mix and I will probably go that route.
<Does tend to be my recommendation. Mollies are fine fish, but you need to work around them.>
In the interim, will the Epsom salt have any effect on the other fish in the tank/ should Epsom salt be a regular addition to the tank?
<Epsom salt won't have any negative effects on the other fish. It IS NOT an substitute for marine salt mix, but rather a laxative that helps relieve constipation. It also raises general hardness, but that's something different to salinity.>
If there are any other compatibility issues I would appreciate further direction.
<I think we've covered everything!>
Not sure of the sex of the gouramis - I was not there when purchased - will attempt to determine
<Your Colisa lalia are males if colourful, females if plain silver.>
I do not use any aquarium salt, should I?
<Some folk do add "teaspoon per 5 gallon" amounts to community tanks but there's not much reason to. Do read here:
Also have not had much luck with live plants (mollies ate everything I put in there - which I understand they do)
<Not normally. They much prefer algae, which is their natural diet. But certain soft plants may be nibbled on. Try Indian Fern, a species that is clearly good to eat but also fast-growing, so tends to hold its own.>
plus most of the information I was given seemed to indicate the conditions for healthy plants were not compatible with
my fish. How important are live plants?
<They aren't crucial at all. Plants provide shade, but you can do that with plastic or silk plants. Plants remove nitrate of course if growing fast, but water changes will do that too. Fast-growing plants do prevent algae though, and that's difficult to do otherwise, so again, clumps of floating Indian Fern can make a huge difference if you're constantly wiping algae from the glass.>
Bubble wall - I am not a huge fan of it esthetically, however if its good for the fish I'll keep it. Recommendations?
<If you don't like it, don't use it! Contrary to popular misconception, bubbles don't "force" oxygen into the water. What bubbles do is move the water from the bottom of the tank to the top. If you do that using a good strong filter, then bubbles are redundant. Switch the thing off, and see what happens. If the fish seem just as perky as before, then leave the
bubble wall off, or perhaps switch it on during hot spells when you worry the water might be holding less oxygen than it should -- you can tell because the fish become sluggish or hang about close to the top of the tank. Do note that Mollies and Gouramis do this naturally, Mollies to breath the air/water mix, and Gouramis to breath air directly, so just because they're at the top of the tank doesn't mean something is wrong.>
Finally, if there are no further compatibility issues, are there any fish species that you would recommend to me.
<I think you have a fine mix of fish! You should add some more Julii Corydoras because they are sociable. Clown Loaches get very big, and also eat soft plants, so I'd tend to recommend Yo-yo Loaches or Dwarf Chain Loaches over Clown Loaches. If you want a livebearer, I suspect either Platies or Swordtails will be better in this tank, depending on its size and how strong the water current is, Swordtails being bigger, more active, more aggressive, and preferring strong water currents. Failing that, Wrestling Halfbeaks are weird and lively, if a bit more difficult to keep.>
<Cheers, Neale.>

Molly Problems -- 10/02/08 Good Morning, <Hello,> I read through almost all of the information here on your site looking for answers to my issues, and as well searched the web for help to no avail. I have a well cycled freshwater tank. It is a Marineland Eclipse system 12 gal. It's been up and running since May of this year. <Twelve gallons is next to nothing in terms of aquarium stocking -- do be extremely careful what fish you add. Even Guppies are too big/energetic for this tank in the long term. Have written much about the problems of sub-20 gallon systems here at WWM, so please do review.> Water quality is near perfect, and I keep the temp around 76-78 degrees with a digital heater. The first fish introduced to the tank about three weeks after set-up were two small fancy fin zebra Danios. <Too active for this tank... need a tank 60 cm upwards in length once fully grown, given their size and boisterousness. Also, they're schooling fish, so groups of six or more essential. In smaller groups they're definitely unhappy (even if you can't tell) and often become aggressive, chasing and nipping each other and their tankmates. Please do get a fish book from the library or book store, and review the needs of fish PRIOR to purchase.> They did very well, and helped cycle the tank. About three weeks later I purchased two red dwarf gouramis. They did exceptionally well, and were thriving. <For now, anyway... Not my favourite fish for lots of reasons.> Finally I added two Cory catfish to help with tank clean-up. <Clean-up is YOUR job, not theirs. Moreover, Corydoras need to be kept in groups of six or more. Few species are small enough for you to keep six specimens in twelve gallons of water. Only "dwarf" species like Corydoras hastatus and Corydoras habrosus would be viable. Peppered catfish (Corydoras paleatus) are the most commonly traded species, but at up to 7 cm long, they're WAY too big for a 12 gallon tank.> All was well until a few days ago I decided to add some Mollies to the tank. I was told by the pet store that adding mollies would be okay, for the other fish I had were community fish. <Again, read a book. Almost all problems in fishkeeping can be avoided this way. Mollies are FAR FROM ideal community fish, not least of all because they need very specific environmental conditions to thrive, ideally brackish water conditions.> So I purchased two platinum Lyretail mollies, and one black Sailfin molly. The Sailfin molly died within 12 hours. She seemed fine, but then I found here floating upside down. That was weird, but I figured maybe she was unstable to begin with and the shock of the move did her in. I pulled the dead fish out and went to bed ( I leave a small red led light on at night so the fish are not in total darkness. good idea or bad?) <Neither, but a waste of electricity so for the sake of global warming, how about switching it off...?> So anyway, in the morning one Gourami was dead, fins eaten, and scales missing, and the other Gourami was being hunted down and eaten alive. <Hmm... could be many things going on here. For a start, two male Colisa lalia will not coexist in 12 gallons. One will become dominant, and the other will be (at best) bullied and at worst stressed to death, unable to feed normally. Next up, mass produced Colisa lalia are of such abysmally poor quality that no-one in their right mind should buy them (at least not without a one-year guarantee!). Have written about this here and elsewhere so do review. http://www.wetwebmedia.com/FWSubWebindex/anabantoids.htm  Thirdly, Gouramis and Mollies have utterly different water chemistry requirements, so anything suitable for one will be harmful to the other.> By the time I realized what was happening it was basically too late for him. He was already battered, and they were relentless in their pursuit. So I pulled him out and euthanized him with seltzer water. <That's not euthanasia, that's a horrible way to go! Where'd that idea come from? It's basically dropping a fish into an acid bath... do think back to your High School chemistry: CO2 plus water = carbonic acid. Nothing there particularly good for giving your fish a painless, rapid death. Do see here: http://www.wetwebmedia.com/euthanasiafaqs.htm > The mollies were acting like a pair of piranhas. Now the next day I notice that one of the mollies lips and mouth are red and swollen with almost bloody spots at the corners of his mouth. His eyes are wide with stress, and he appears to be in pain. What is going on here? <What's the water chemistry? Be under no illusions here: Mollies MUST HAVE hard, alkaline water around pH 7.5-8.2, hardness 15+ degrees dH. They are infinitely healthier in brackish water around SG 1.003 upwards. They are extremely intolerant of ammonia, nitrite, and even nitrate. Being herbivores, they will not stay healthy given a non-herbivorous diet. All these things are amply discussed in the literature and here at WWM. http://www.wetwebmedia.com/FWSubWebIndex/mollies.htm In small tanks they never do well because of their sensitivity to rapid pH changes and nitrate accumulation. Even 20 gallons is too small for them, especially given some varieties will reach 10-15 cm in length. Recommend not less than 30 gallons if you want even half a chance of keeping Mollies properly.> I left him in the tank to watch to see if the culprit is the other molly attacking him, but she never touches him. She swims near then darts away. Within a few hours this molly is dead. So I have now just one molly and my cories. Now today I notice that her mouth is swollen and pink. Her lips are bumpy rather than smooth, and she is acting weird. <Could be Mouth Fungus (also known as Columnaris) but equally easily Finrot or even incipient Fungus. Extremely common when Mollies are kept in freshwater conditions. Just to make this point clear to all our readers -- Mollies just aren't "good" freshwater aquarium fish, and inexperienced aquarists should NEVER keep them thus. Stick them in a brackish water tank and they're tough as nails, and in saltwater tanks can be used to cycle filters from scratch! All good clues to what these fish actually want, as opposed to what we sometimes try to foist onto them.> Just sitting stationary in one corner near the heater. <Likely "the Shimmies", again, very common.> I've never seen a problem like this, nor seen mollies act so violently. <Unlikely the Mollies killed the Gouramis, though adding new fish to an overstocked aquarium could easily tip the balance such that the "surplus" fish died. That said, male Mollies are mutually aggressive, and again, that's why they need BIG TANKS.> Can you please give me some advice, for it looks like I'll be restocking soon for all my fish have died. I am at a loss. Help! Thank you!!! <Please, first thing you do is grab a pH and hardness test kit and establish what your water conditions are. Then go read a book of fish species, and when you see a species you like, cross-check its requirements with what you have in your tank. If you have soft, slightly acidic water, then tetras and barbs will be fine, but livebearers and many cichlids won't be appropriate. Do see here: http://www.wetwebmedia.com/FWSubWebIndex/fwlivestk.htm http://www.wetwebmedia.com/FWSubWebIndex/fwlvstksel.htm http://www.wetwebmedia.com/FWSubWebIndex/fwlivestocking.htm Now, I'll tell you that in a mere 12 US gallons your choices are extremely limited for all kinds of reasons to do with activity, adult size, sensitivity to pH changes, and so on. Avoid anything above 2.5-3 cm in length, and don't pick anything noted for being either aggressive or an active swimmer. Neon tetras, gobies, Kuhli loaches, pygmy Corydoras species, shrimps and snails are all good choices for very small tanks.> Joanne from New Jersey <Cheers, Neale.>

Sick Molly... env., mis-mixed with goldfish  12/07/2007 First I would like to thank all of you. Any time I have a question some one always answers me. So thanks. Now onward. I have a 10 gallon tank. I have 3 mollies and 4 goldfish. Now I know they like different water situations and found this out after the fish were bought and put together (need to do my homework, I know). However, every fish was doing fine but now ALL my mollies have what appears to be fluffy white spots on them. Not sure if it's a bacteria or a growth...what can I do? Also is the water contaminated now to, so if something does end up happening to my molly's will it contaminate the next fish? Thanks so much. Laura <Hello Laura. The Mollies have Finrot and/or fungus and need to be treated with a combination Finrot/fungus medication. This is extremely common when Mollies are kept in freshwater. In addition, Mollies are acutely sensitive to Nitrate, and Goldfish are veritable Nitrate factories! So you WILL need to separate them. Please do read our article on Mollies and act accordingly: http://www.wetwebmedia.com/FWSubWebIndex/mollies.htm Hope this helps, Neale.>

Molly Flashing  11/28/2007 Hi. I have a 10 gallon aquarium that I use for Molly fry. I've noticed that the fry like to bounce off the rocks in the tank. They're not rubbing their bodies, just a quick rub of the head area. Most of the fish in the tank do this at some point. They all appear healthy, are growing and feeding vigorously. We have only lost two babies out of approximately 50 that have passed through the tank since July. Is this behavior normal or a sign of a parasite? Thanks, Joyce <Hello Joyce. Are you adding marine salt mix to the aquarium? And what's the water chemistry? Mollies (and indeed most other fish) scratch their bodies when they are irritated. Sometimes this can be a sign of illness, specifically parasites that attack the skin and/or gills. But it can also be an indication of water chemistry issues, particularly excessively low or high pH levels. Just to recap, Mollies need very hard (ideally over 20 degrees dH) water and a pH of not less than 7.5 and ideally around 8.0. While not all Molly keepers agree, there's a widely held view that adding marine salt mix to the aquarium is beneficial. Wild Mollies are common in brackish water habitats, and when kept without salt in the water it is common (if not universal) that Mollies become more sensitive to infections such as Finrot and fungus. Salt also reduces the toxicity of nitrate, which Mollies appear to be extremely sensitive to. Marine salt mix (as opposed to generic aquarium or tonic salt) contains carbonate salts that raise the hardness and prevent acidic conditions in the aquarium, and this also has a dramatically beneficial effect on Molly health. From my experience, the vast majority of instances where people have Molly problems, those people are keeping them in tanks without marine salt mix. I'd recommend adding 3-6 grammes of marine salt mix per litre of water, and then seeing how your fish do. Cheers, Neale.>
Re: Molly Flashing 11/28/07
Hi Neale. Thanks for replying. I guess I should have listed the water conditions in my first email. All levels are good, (PH around 7.9), our water is naturally very hard and alkaline. <Excellent.> We do 20% water changes once a week. <Ramp that up to at least 30% per week and ideally 50%. Mollies do not like nitrate, and it seems to be one triggering factor being ill-health.> I've heard that Mollies prefer saltier water, but we have two small Corys in with them, so don't want the Corys irritated. <Fundamentally Mollies and Corydoras can't be mixed. End of story. It's a shame people sell Mollies as "community fish" because they're not.> What has me curious is that none of the fish seem stressed or sick. They don't rub, just bounce off their heads. The two five month old males that are in the tank are gorgeous and lively, but they too flash off the rocks once in a while. I'm thinking if it was a parasite or illness, these fish should show some sign of it by now. <I agree, but what you're describing simply isn't normal. Hence the need to try and narrow down the possible causes. Parasites on the gills (typically Ick or Velvet) plus improper/fluctuating pH are the classic causes of "flashing" behaviour.> So the water conditions sound more likely, even though the numbers are good. <Do check the ammonia and nitrate levels, if you can. While nitrite is the thing people usually check first, with good reason, nitrate especially is something that you have to watch with Mollies.> Hmm, will have to investigate that possibility more carefully. Thanks for your help. Joyce <Good luck, Neale.>

Male molly  2/12/07 I apologize now for this question may sound like a windup or something purvey, I have a black male molly who has been in the tank for nearly a month, throughout this time he has basically been a sex-pest to a female molly who he shares with a subordinate orange male, <A bad sex ratio for poeciliids...> until recently, she has been the only fish the male has been able to harass; recently I have introduced two female molly/ platy crosses for him to harass. <Oh! Good> the other day I noticed he (black dominate <dominant> male) was hanging round at the bottom of the tank, 'hiding' nearly out of site, <sight> when he moved and was visible, and this is why I don't want to sound funny, his 'Gonopodium' (genitalia) which normally sits back or extends round when he is copulating is now permanently sticking out from his body at an odd angle. it also appears that a small black lump on the end of his parts has appeared, though this could be normal as it is his normal coloration. his character has dramatically changed, he hides a lot and he avoids brushing 'it' on things in the tank. I would have used the forum chat, but ppl might accuse me of being some sort of pervert. has he really injured 'himself'? <Does read as such, yes> is this a common problem? <Not atypical> what can I do? <Hope, be patient...> I can send pictures if this helps but I have as yet been unable to find anything on search engines which doesn't bring up obscene porn or strange blogs mike <Thanks for sharing. Bob Fenner>

Sick molly - disappearing Betta 7/9/07 Have been reading your website - but nothing seems to apply exactly to what's going on with my fish. <OK.> We have a ten gallon aquarium which we started with a male beta he lived there for a few weeks with 4 plants in peace and harmony - then we brought home from the store 2 Creamsicle sailfin mollies and a snail. One molly had a pale patch of scales on it's head, but we had seen others in the tank with the same markings so we thought it was a normal color variation. After adding the new fish we noticed the larger female molly without the pale spots was frequently attacking the other molly it seemed to have ideas of attacking the beta - but of course the beta wasn't having any of that! <A bad combination of animals. Apple snails almost never mix with fish because they get nipped, and after a while they die, polluting the tank. They're also subtropical -- not tropical -- animals and get heat exhaustion in the long term. Mollies, contrary to myth, do best in brackish water. Bettas (not betas) need freshwater conditions, and are essentially incompatible with mollies. Mollies are also far too big and active for a 10 gallon tank. So right out of the starting gate there's problems. Did you do any research before buying these animals?> The next morning we noticed the beta had a split in his tail and the smaller female molly also had a piece out of it's tail so we returned the aggressive (?the healthy one?) fish to the store. <Hmm...> The betas fins continued to rot away - but the molly's seems to be growing back for awhile. Beta occasionally chases and nips at the molly still. <Did you do anything to treat the damage? Adding finrot remedy after fin damage is absolutely essential. Fish are swimming about a warm, bacteria-laden soup and can't help but get infected if they're immune system is at all compromised.> Now they both look awful - the beta's tail is nearly gone - I don't see any white patches on the beta though and he still flares at the mirror and swims around normally and chases the molly. The molly has large chunks out of her tail, the pale spot on her head is paler and I can make out a couple more pale spots by her dorsal fin perhaps a bit pinkish? The scales on the top of her head look uneven like sheets on an unmade bed - she has a red spot on each gill though seems to be breathing normally - she is wasting away very skinny and has no energy - sometimes floating or swimming around listlessly with her nose up or being bumped into the floor of the tank by the filter current. Her body occasionally twitches or shakes. <The molly is obviously dying; she has a combination of finrot/fungus plus something called "the shimmies" which is a neurological condition brought on by poor healthcare. Doesn't happen when they're kept in brackish water, but I guess that horse has left the stable... She's dying, so may as well euthanise her painlessly.> The both swim to the top and seem to be starving at feeding time but then when I put the food in they don't seem to see it and are lucky to get a piece before it floats away. <Maybe they don't like the food you're giving them? Mollies are primarily herbivores, so algae-based flake plus stuff like Sushi Nori are what they need. Bettas feed on insect larvae, and (wet) frozen bloodworms are the ideal for them.> Do you think it's columnaris introduced by the new fish? Should we separate the molly and beta since the beta is not as sick and treat them separately? <There's a whole bunch of things going wrong here, but the problem is you, not the new fish. You've bought a collection of incompatible fish, kept them in a too-small tank, made no attempt to provide the correct water parameters for the mollies, and apparently not treated for any of the diseases.> Ammonia and nitrites are 0 - nitrates are 20 - temp 80 - pH 8.2 <The pH is way too high for a Betta, and the nitrates way too high for mollies. Bettas need around pH 7.0, mollies around pH 7.5-8.0. Mollies in freshwater conditions need ZERO nitrates, but in brackish/marine conditions are much less fussy.> 6 plants now and the snail is fine except the beta has bitten off his antennae! <The snail will die soon. When the antennae get nipped this is a sign the apple snail is being harassed. As sure as God made little green apples this poor old snail will be increasingly stressed. After a few months it will die. Apple snails simply aren't good in tropical aquaria. In subtropical aquaria maybe, but not tropical aquaria. Max temperature is around 75 F long-term, but ideally a bit less even than that.> we heard you could keep a beta with some other fish but ours doesn't seem very sociable <Most Betta owners keep them in their own aquaria or with peaceful bottom dwellers such as Corydoras and Kuhli loaches.> also we will be moving cross country in a month - do you have any tips for the best way to transport fish tanks in a car? <Place fish into sealed bags or buckets about 1/4th filled with water and the rest air. Insulate the packages with towels or something similar to keep them warm. Your local aquarium shop may be able to provide you with the polystyrene containers they receive fish in. These are perfect for the job. Cheers, Neale>
Re: sick molly - disappearing Betta  7/10/07
Hey Neale <Hello Ruth & Eric,> Thanks for your assistance. <No probs.> I'm surprised to hear that mollies shouldn't go in with bettas as we actually did research it before buying them and several sites specifically suggested mollies as good tank mates for bettas because they both like hard hot water. <Well, no disrespect to the source you read, but the fact I know better is why I write aquarium books and for aquarium magazines. I don't make this stuff up to annoy people! Mollies like water that is hard, preferably brackish, and with a pH around 7.5 to 8. They do even better in seawater. In terms of temperature, something around the 26C/79F mark suits them well. Bettas are classic labyrinth fish and have evolved to live in hot, humid places where their air-breathing 'labyrinth organ' helps them get oxygen from the atmosphere because there isn't enough in the water. Anything up to 30C/86F will suit them fine. In terms of water chemistry the ideal is soft to moderately hard and around pH 7. In other words, much like barbs and tetras.> However I think we should have gotten the smaller short finned variety as soon as we put these in the tank we could see the tank looked crowded. We have been adding 1 tsp of aquarium salt for each 5 gallons but probably should have been more for mollies? <To be honest, this is like trying to make an "happy medium" that will suit camels and penguins. It can't be done. Mollies want a completely different aquarium to Bettas. Mollies need lots of swimming space, a fairly strong water current, plenty of depth, and they need to be kept in groups to avoid aggression. Bettas live in swamps and hate strong currents, and they need tanks with lots of plants so that they are always near cover. Bettas are slow moving and feed at a snail's pace, Mollies wolf down food as soon as they see it. Bettas are carnivores and like plants for security, Mollies are herbivores that simply eat plants as food. Adding MARINE salt mix (NOT "aquarium salt" or "tonic salt") will help Mollies a great deal, but at the dose your Mollies require for health, your Betta will be stressed, probably die. So what can I say? There's really no way you can please both these fish at the same time.> The water comes out of our tap with a very high pH - maybe we should add a piece of drift wood to bring it down a bit? <No, don't bother. Messing about with pH unless you know what you're doing usually ends in tears. Much better to accept the water conditions you have, and in future select fish suited to it. If you have very hard and alkaline water, then stick with livebearers, rainbowfish, cichlids, etc that enjoy such conditions. Your fish will be healthy, happy, willing to breed, and easier to keep. Problem solved.> The snail was more of an impulse purchase - we didn't realize they don't like hot water! <Lots of people make this mistake. Apple snails come from Florida, which isn't hot all year round as you know, and in the wild Apple snails "aestivate" during the summer. That is, they go into a resting phase. Without this resting phase they simply "wear out". This is why so few Apple snails last long in regular aquaria. For most people, they only last a year, if that. Kept properly, they live for many years and reach enormous sizes. One at the London Zoo had a shell that was bigger than a tennis ball!> Or that the betta would nip his antennae. <Yup.> He seems very happy he's so active and moving around the tank all the time - the molly does not harass him. <Snails aren't very smart, so don't expect to see any signs of stress as such. It's not like a fish that goes and hides in the corner when it's unhappy.> How can you tell if your snail is sick? <Usually, they die.> Will they become sluggish? <Don't bank on it.> Ours moves around like a little race car. <Yup! I've kept and bred Apple snails and adore them. The babies are amazingly cute. But there's no escaping the fact they need their own quarters, or at least a subtropical aquarium with suitable fish.> We had read that the best first step to treating fin rot was to do frequent water changes and add salt so we tried that first. <No idea why that was suggested. Salt can *prevent* secondary infections setting in when used at a substantial dose (around 1 gramme per litre upwards). But it cannot kill off an infection once one has set in. Otherwise marine and brackish water fishes wouldn't get finrot, but they do (though admittedly not commonly). Really, the only cure for finrot, which is bacterial, is the use of an antibiotic or antibacterial medication. There are many of these available. Dipping freshwater fish into seawater for short periods can also help as a therapy, but raising the salinity to that level in the actual aquarium would be lethal. Apple snails, incidentally, are likely respond poorly to most medications, so check before use or remove to another tank during the treatment. Finrot almost always follows on from physical damage and poor aquarium water quality, so check these factors as well as treating the symptoms.> Last night before receiving your reply we decided we had to do something so we got a divider to prevent the molly from being harassed did another water change and added tetracycline to the water. Now the betta looks quite happy and is enjoying his own little partition of the tank where there's nearly no current because of the divider. <Indeed. Betta may be happy, but the molly won't be.> He's eating like a piggy and flaring at his mirror I think he will be fine - I did notice some trailing white fuzz from his fin today which makes me think maybe it's Flexibacter? <Quite possibly.> The molly just looks worse though lying at the bottom of the tank panting - I feel like we should give her every fair chance to recover though. My brother thinks the tetracycline made the molly worse and we shouldn't add any more of that - I think the molly would have gotten worse anyway and that we should finish the treatment to get rid of the stuff if they are going to have any chance of recovering. <The tetracycline should be fine for the molly. The problem is, and I keep coming back to this, but everything you do to make a good aquarium for a betta makes a worse one for a molly.> We actually did tons of research on this tank - but it seems like you get different answers from every site you see so it's hard to know which one is right! We read the articles on your website as well as many others. <I've never written anywhere that Mollies are good with Bettas. Within the hobby, I perhaps have a reputation for being a bit hardline on this, but frankly I don't consider mollies freshwater fish at all, at least not in the sense most aquarists mean. Yes, they live in freshwater in the wild, but in aquaria Mollies kept in brackish water simply do better, live longer, and are less disease-prone than Mollies kept in freshwater. Period. End of story.> Actually the article on wetwebmedia by Bob Fenner suggests mollies as good tank mates for bettas. <Bob and I will have to agree to disagree here.> We had a lot of algae in our tank and wanted something that could gobble it up and the mollies had it clean in 2 days! <Yup, that's what mollies do. They're herbivores.> We have flakes for the betta - maybe we'll go get some frozen bloodworms too - we weren't sure what kind of meaty food to get him since we read somewhere that the freeze dried ones aren't properly disinfected and might put disease in the tank - and we have algae based flake food for the molly - she seemed to like it but then she sometimes would spit it out so maybe we should just try a different brand for her - if she recovers that is. I think the betta perhaps just couldn't get to the food because the filter was shuffling it away too fast - so we'll feed with the filter off from now on. <I abhor freeze dried foods with a hatred that cannot be described. I have yet to see any fish prefer them to wet frozen foods, and I personally have never kept any fish that would even eat them. I have no idea why people buy them. Wet frozen foods are healthier and the fish much prefer them. So do yourself a favour and skip the freeze dried rubbish.> Thanks for your input and will be glad to hear any further comments. Ruth and Eric <Bottom line, I think your Molly is doomed. Your intentions are all laudable, but in this instance I think you received some flawed information. Bettas are simply easier kept alone with ZERO tankmates. If you want to keep Mollies, then set up a 20-30 gallon tank just for them, and keep it at a brackish water salinity (SG 1.003 - 1.005 is ideal). You will be STAGGERED at how much healthier mollies are under such conditions. Also, consider buying a book. Web sites are all very well but there's no quality control. But books from reputable publishers in the field like TFH and so on will have stuff that's been edited and fact-checked. Good luck. Neale>

Sailfin (Molly) with Fin Rot? No useful info.  3/6/07 Help - my 4year old sailfin has seemingly overnight lost half of his dorsal fin and now his tail fin is looking ragged. I treated with Melafix <Worthless> a couple of days ago but I think it's getting worse. Today I noticed a red tailed shark also has a ragged dorsal fin. I haven't added any new fish for a while - mainly African cichlids which have been in with him for a couple of years. <Yikes... incompatible> I did add a Red Terror a few months ago who has grown quite quickly. Could he be tearing up these two or more likely fin rot? <Possibly, yes... more likely stress induced... environmental> Unfortunately I don't have a spare tank so if you think it may be aggression I will have to move Terror on. Hope you can help, Thanks Lisa <Uh... where's the boeuf? Information re your set-up, maintenance, water quality tests, feeding... Please read here: http://www.wetwebmedia.com/FWSubWebIndex/mollydisfaqs.htm and the linked files above... Bob Fenner>

What Were You Thinking??!! Hi my mollies have been die with no clue as to why! Well I have 7 mollies 2 males and the rest female. First one large molly (I think it way pregnant but I don't know how to tell) fell to the floor of the tank and seem to have trouble breathing and was upside down (belly up) and died soon after. No signs of disease! Then one male yesterday did the same thing two weeks later. The water is cloudy too. Now here the tanks set up: 5 mollies  one male two females 10 Zebra Fish 3 gold fish 3 black Moor gold fish 6 neon tetras 1 peacock eel 5 guppies( just had 20 babies I keep in a small tank) 1 upside down cat fish 1 glass catfish 1 Raphael cat fish 3 silver hatchet 2 cat fish that I don't know there names 2 plants of one kind 5 plants of there other 1 of one kind! A bio filter 1 old fashion filter( plastic box with carbon and white foam filter) 1 small tank filter 2 castles ¼ inch gravel All this in a 10 gal. I don't know what I was thinking? Is this good or bad? How do I keep my mollies healthy? How do I keep the others healthy? Can all the animals live with one another? Help I have no clue on anything? <I count 41 fish in a ten gallon tank!!! And another 20 fry in an even smaller tank! This is what you MUST do. Return all the Goldfish, all the Catfish and the Eel! (OMG, an eel too!) Then out of the rest, pick your favorite five. Return all the rest. If any of the Catfish are Corys you can keep them, but they count towards the five. All the others must go. You have no chance of them living let alone being healthy. To say you are grossly overstocked is a gross understatement. You can also keep the castles, but I wouldn't. Don>        

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