All 4 tanks in my home contain at least one or more mollies, they're awesome. Mollies were one of my first fish (one black sailfin, one plain black). Since then, I've had about 70-80 babies. I'd say about 60-70 of those babies came from my sailfin molly mother, as opposed to the numerous balloon mollies that I have as well. The only time I have successfully captured the babies of a balloon molly were when the molly had babies the same day I purchased it. Since then, I've had no luck, considering the difficulty to see whether or not a balloon molly is pregnant. I have a 'breeding tank' now and it is filled with java moss and other plants that help the fry hide. The strangest incident, however, is the female platy I have in the breeder tank. There are no male platies in any of my tanks and I frequently see my black molly (non balloon) chase the platy and "mate" with her. He mates with no other fish, including the other female black molly. I'm hoping I'll have a strange strain of fry.
I love Mollies. My last pair had about 20 fry that all survived! Out of that batch I kept two, who I affectionately call "The Twins". They are two marble Molly males but with a touch of golden color on their tails. They were the only ones like this from that batch. They are mirror images of the other. They are very busy boys and keep my females very busy!
After much experience with this beautiful fish, I would like to offer some advice to those looking raise them. Add a little sea salt to their water (about 1 tsp. per 20 liters). I have a 100 L community tank with fancy guppies, lyretail mollies, and cory cats in it, but tetras will not tolerate these water conditions. It is better to transfer the fry to a 40 L tank with similar water chemistry (pH 7.5, KH 8, 26°C) when born, rather than try to use a breeding trap. Keep lots of live, leafy plants in the tank, as mollies are vegetarians, and will eat the algae off of them.
Mollies can get territorial and my orange lyre tail molly was at one stage killing off any new male addition to the tank. He didn't bother the juveniles that grew up in the tank funny enough. I added a black male to the tank recently and it took some pecking before the new boy knew his place and cowtowed to his orange majesty.
According to all books I have read, Black Mollies are not good beginner fish. Here's why: Black Mollies are more susceptible to disease than other mollies, especially to the disease Ich. I had black mollies and the female got Ich because the water put in the tank was slightly cooler than the water already in the tank (none of my other mollies got Ich, however). My black male molly was such a bully that I had to take him back to the store. Also, don't use Black Mollies to break in a tank; they will most likely die.
I live in Japan and can find Mollies in any pet store. They are the japanese goldfish in my opinion. These fish can be bought in oranges, whites (non-albinos), and, of course, black but these are normal shapes or ballooned. Their stomachs look like they have swallowed mini-golfballs. I own two and they are approximately 2 cm, with very little personality compared to normal mollies. I like them, but they also appear to have poor immune systems because every other week they have white spots on them. I don't know everything about fish, but they are of moderate attention needs.
Despite raising fish for almost 25 years, I have had only modest luck with raising black mollies (plain, lyretail, etc.). I learned the hard way a long time ago that these guys require two additional components not necessary for other livebearers: increased salt and a vegetarian diet. For sure, black mollies will not only live, but thrive, in saltwater tanks. Pure freshwater is a no-no. Balloon mollies, on the other hand, seem to remain hardy in less molly-friendly conditions. This is to say that they do well in my 75 L community tank where they share their abode with neon tetras and a pair of veiltail angelfish. No additional salt has been added, although I do supplement their diet with both standard flake food and a molly formula spirulina flake. Despite being a freak fish, balloon mollies just may prove to be a better choice for the novice aquarist than their less deformed kin.
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