I hadn't been looking for a second sword, hehe!
So, female livebearers have anal fins, males have a modified anal fin which is called a gonopodium. My the way, males which start growing swords later in life apparently turn out to be more impressive.
I would love to have more Cory Cats but I think I would be terribly overstocked in my 16 gallon. Would I?
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I have an identical 16 gallon set up on the other side of the room with 10 White Cloud Mountain Minnows and 5 Corydoras Sterbrai and all are very healthy. I will try and add some pics of the tanks soon.
To be honest I wouldn't keep any of the fish you have in anything under a 3 ft long tank as I prefer to give my fish more swimming space, but the numbers of the minnows and swordtails you have are good for a small community. Corys are also schooling fish, like the minnows, so also do best in larger groups, which is why I personally would not keep any, if I couldn't keep 6 or more.. but that doesn't mean I won't keep any of those type of fish: for example, I would have chosen guppies of platys instead of swordtails, dwarf danios instead of minnows, dwarf Corys instead of medium and large ones.
In terms of what you can get away with, that very much depends on the exact set-up you have, but you are right you may be overstocked with more fish and you should also keep in mind that once the swordtails start dropping fry, you can expect 50-150 babies per female every 4 weeks. Unless you have something to do with the babies, the tank is very likely to become very overstocked quickly. If you haven't planned this far ahead, it's probably worth keeping the swordtails on the peckish side.
If you have too many swordtail males, another option would be to return some of the males and replace them with more Corys, to get the numbers at least up to 6.
As for the Swordtail I lost, other than stress I can't think of another reason I would have lost her? She was more sluggish than the rest so maybe she had other problems. The rest of my swordtails appear healthy.
It can be stress, but stress can be caused by many different factors. So you shouldn't be asking "did they die because of stress?", but "if they died because of stress, what caused the stress? was it anything I could improve on?".
Off the top of my head, these are all stress inducing conditions for when one buys a fish:
* was the fish with appropriate tank mates at the LFS?
* was the fish feeding well at the LFS?
* had the tank the fish came from been infected with anything recently?
* was the fish stressed when it was caught out?
* was the fish exposed to high/low temperatures on the way home?
* was the fish in a dark environment on the way home?
* how did you acclimatise the fish?
* are your tank water parameters the same as the shop?
* was the fish stressed by your tank environment?
* did anyone disturb the fish after it was added to the tank?
and so on.. all of these can cause "death by stress", but some of them you control and some you don't. On top of that, it is possible that the fish had only recently recovered from a disease or had some long term health problems, and it is impossible to know if any of these affected it.
You mentioned that she was sluggish, how so? Did you notice it at the shop? If you don't already, it is well worth observing the fish you are thinking of buying for at least 5-10 minutes before picking the ones you will take. It is also worth checking that tank, that tanks to the right and left, and those on the same filtration system for signs of unhealthy fish. If you spot a problem in any of them, come back another day.
What should I do? The fish, at least at the moment all seem fine together, and the tank is well planted and gives plenty of hiding areas. I don't want to add more females as I'm worried the tank would be over stocked. Should I hang on and see how they behave together? Or should try and give away 1 or 2 of the males and replace them with females?
Now that we have some more information, my recommendation would be to either take back all males, or almost all, and replace them with 3 more Corys of the same species.
