dying livebearers

[maranatha22859]

I've been keeping fish for about 6 months.
I've got a 5 gal quarentine(sp?) tank and a 10 gal tank. I do 20% water changes weekly. I add salt as I only have livebearers. I also add stress-zyme with the water changes. I check the water chemistry with water changes. I feed once a day with fish flakes and occ with dried BBS. Both have never had any more fish than they do now. Both tanks are planted and have the same parameters:

Ammonia -0
NitrAtes -20
NitrItes -0
pH -7.8
Temp 78

I currently have 2 female and 1 male guppies, a small cory, and 1 male/1female baloon mollies in the 10 gal tank (as well as some fry.)

There's 1 male platy and 1female rainbow swordtail in the 5 gal.

Here's my problem: Over the last 8 weeks or so, I seem to be losing an average of 1 fish per week. A couple of them suddenly had problems swimming straight-sort of leaning over at times. They died after a few days or a week. The others seemed to get light blackish patches near their heads and back. I found a female platy had died while I was at work. In the morning she was acting normally and appeared to be ready to drop, but when I got home, she was dead and was thin, and had lost a lot of the orange part of her skin. She's one of the ones that had this black patch. I lost 1, but saved another from fin rot with a sulfa antibiotic. I just started using the quarentine tank about a month ago. I've been adding Melafix to the tank for the past few days when I added the platy with a swim straight problem, and the next day the sword with the black patch. The platy is about the same and the sword seems a little better, but I'm not 100% sure.
Is this to be expected with livebearers? Any ideas?? Do I have a water problem that's not showing up on the tests? Am I being overly vigilant? Everyone I know that has fish just sort of leave them alone. Feed them every day or two and change the water every few months, and their fish seem to do fine! Or do I just have poor quality fish? Our only lfs that's not a chain doesn't sell guppies, and has very few livebearers, so I've gotten them all from Wal-Mart, PetSmart, and PetsPlus. The longest one I've had died last week -I had him for about 3 months. Thanks for the help and sorry for the long post. I wanted to be thorough!

 

[William]

Well, the water readings are absolutely perfect

Livebearers do have a relatively short life however they should live longer than just 3 months (+3-5 months while they were grown for the shop to sell) . They usually live about 18 months. I can't see why they would suddenly start dropping off like this, you mentioned one which was pregnant which died which does happen because it is quite a stressful process for them, as for the others were they all females? You say that you've been losing a fish a week for the last 8 weeks, thats 8 fish, have you been restocking your tanks since then or did your tanks originally have 8 extra fish in them?

Where these fish used to 'cycle' the tank which some people believe may weaken the fish and also it could just be that they were poor quality fish anyway. Unless they had some form of internal infection, give me some time and I'll put my thinking cap on.
Cheers and good luck

 

[maranatha22859]

Thanks for the reply! I have been restocking. My first tank was the 5 gal, which I made the quarentine tank when I got the 10gal. I've kept the new fish in the 5 gal for a week or two, and only moved them 1 or 2 each week into the 10gal. I've never had more than 1 fish/gal in either tank.

I've lost the original fish which I used to cycle the 5 gal. At first, I lost a few females, right after they dropped. I didn't give it much thought, thinking it was due to stress. Lately it's different, and I've lost both males and females.

I started the 10 gal with substrate, water, and filter and the fish from the
5 gal.

It's probably dumb to even think about this right now, but I was planning to get a 55 gal next week. I was going to cycle it the way I did the 10 gal, but I figure I'll try to go fishless -No need to possibly contaminate a big one!