Sacramia

Ok I have a 10g tank that I set up just after Christmas and it has been running ever since. I was wondering what is the max number of fish I could have in it? They are all small fish. I have 14 right now, and im not planning on getting anymore.

When I first got fish I got 2 Dalmation Mollies and 2 Swortails (1male and 1female on each). They were doing great untill the 3rd day or so and then the male swordtail died and then the rest. So I went and got my water tested and I guess it wasn't stable yet or something. So I let it cycle for about another month or 2 and then i got 2 Sphenopp mollies (idk how to spell it). I think one was male and the other female. But one of them attacked and killed the other. I know the males have the anal fin that never comes down but do females fin go up like the males as well or does it always stay down?

Also, if my fish were to breed, I dont have another 10g tank. I have a 2.6 liter tank, or something like that. Would that work for the fry?

sirdarksol

First of all, welcome to Fishlore.

As far as your tank goes, it is, I'm sorry to say, horribly overstocked. The general guideline is one inch of adult fish per gallon of water. The livebearers you have (mollies and swords) grow to 2-3" apiece, sometimes more. The tetras and danios can range from 1-3". With 14 fish, this puts you at way over the guideline. In addition, mollies prefer to have a lot of swimming space for their size (particularly vertical swimming space, which isn't available in a 10g).
Unfortunately, your fish will not be happy in the current setup. A small school of the head and tail lights would do okay in the 10g, but most of the other fish would do better in a 20g tank or larger.
The options, as I see them, are as follows:
1)get more tanks. A 30g, combined with the 10g, will probably do okay to split the two groups of fish up.
2) Find new homes for most of your fish. This one is probably the most preferable, as you don't have space for the livebreeders to breed. They'll quickly overstock your tanks again.
3) Keep them in this setup. They will die of stress and nitrate poisoning. You can slow this down with frequent partial water changes, but nothing will stop it completely.

Lastly, as far as what happened with the fish at the beginning of the tank's life, it's likely they died of ammonia poisoning. The following article describes the nitrogen cycle, which is what turns ammonia (body waste. It's in the urine and feces of most creatures, both terrestrial and aquatic) into nitrates, which are less toxic (though not completely non-toxic)
http://www.fishlore.com/NitrogenCycle.htm

I'm sorry to give such bad news. Unfortunately, the people who should have been educating you about these things (that is, employees at the store you got your fish from) are more concerned with a quick sale, or maybe just when their shift ends, than they are with your aquarium (or anybody else's) succeeding.
If you have other questions, please feel free to ask. Unlike fish store employees, our number one concern is keeping you happy by keeping your fishy friends happy and healthy.

COBettaCouple

Welcome to Fishlore. SDS' advice is the same as ours and I'd recommend a much bigger tank as soon as possible.