Swordtails

Hi Andy,

I've seen your post in the Introduce Yourself thread, and notice that you say you are new to fishkeeping. Just so we don't miss anything, I'm going to ask you some questions, and if you could answer them it will help.

How big is the tank?
How long has it been set up?
How did you set it up - let it run a few days then get fish, or do a fishless cycle using ammonia/fishfood?
Do you know the readings for ammonia and nitrite in your tank?
Did the fish show any signs of being sick before they die eg spots, ragged fins etc?
Have you only had one male swordtail at a time?
What kind and how many other fish do you have besides the female swordtails?

I do have reasons for asking 

Swordtails grow quite big and need a fairly large tank, and male swordtails can be pretty nasty towards each other, so unless the tank is huge, only one male should be kept.
A lot of shops tell you to let the tank run a few days then get fish, often selling you a bottled bacteria product to add. They don't usually bother to tell you that those bottles of bacteria commonly don't work and that you need to do water changes, a lot of them, to keep your fish healthy.
If the tank is very new and if you didn't 'cycle' it for several weeks using ammonia or fish food, you will have ammonia and nitrite in the water which will harm the fish, unless you have been doing very frequent water changes to keep them low. Some fish are more susceptible to high levels of ammonia and nitrite than others.
You may have other fish which don't get on with swordtails - and as the males are a lot more aggressive than females it could lead to fights.
The fish could have been sick when you got them. Any signs on their bodies would help ID a disease, though there are some that don't show external signs.


If you can give as much info as possible, it will be a great help.

Can I suggest you ask your father to check your ammonia and nitrite levels again asap. They would have been OK before you got your first fish because it is the fish that exctrete the ammonia.
As soon as you put the first fish in, they would have started excreting it immediately (it's the fish version of urine). Because the filter was brand new, there would have been no bacteria in it to eat the ammonia so the levels would have built up quite high. Unfortunately, ammonia is toxic to fish, it burns their skin and gills. Eventually, some bacteria grow in the filter and they turn the ammonia into nitrite, which is also toxic, and would also start to build up. Eventually, a second type of bacteria grows which turns nitrite into nitrate. This is only toxic a high levels, and is removed by weekly maintenance water changes.
Because both ammonia and nitrite are toxic, they must be removed by water changes before they can harm the fish. Both need to be kept below 0.25ppm while the bacteria grow. Once there are enough bacteria, after several weeks, they'll remove the ammonia and nitrite for you.

Since it is now six weeks since you got the first fish, you should have grown aomost all the bacteria you need by now, but it is still worth checking the levels, and do big water changes if either ammonia or nitrite read above 0.25.


As for your fish, I wouldn't be surprised if the tiger barbs had something to do with the deaths. Your neons, glowlights and the barbs are shoaling fish, and need to be in shoals of at least 6 each. Tiger barbs have a bad reputation for aggressiveness, and are worse the fewer there are. The recommendation is that 10+ are needed to keep the aggression between themselves, which is too many for a tank your size.
This is your tank and you will have your own fish preferences, but if this was my tank I'd see if the shop would take the barbs back, even if they'll only give you a credit note for them. Then, once you know your ammonia and nitrite levels are staying at zero, get a few more neons and glowlights to make their numbers up to six each.
As for the swordtails, you have time to decide what to do about getting another male. Just one as your tank is too small for two of them, they'll probably fight. One thing to bear in mind is that your females have been in the same tank as a male. Therefore they will be pregnant. Before long, your tank will have a number of swordtaill fry in it, and they'll both continue having fry for several months as female livebearers can store sperm. If you have any plants, live or synthetic, some of them will survive. And you may well find that any surviving male fry will be healthier than bought ones.