cosmic dust

Sorry for a long post.....
So my 30 gallon cycled - I saw the ammonia, then nitrites, then both went to zero & I thought I was good to go. I'd added the tap water conditioner when I put the water in. I did a small (10%) water change last Monday to get rid of some of the nitrates (down to 5ppm) and added 6 zebra danios (by the way temperature 78F, pH 8 - 8.2, very soft water)
That was last Thursday. On Sunday, I did another 10% water change. I didn't turn off the filter while I was doing it & when I got done, I found one of the fish was stuck to the intake of the filter. I quickly turned the filter off and the fish swam away....but it started staying at the back of the tank & not moving much, its tail rising higher than the rest of it. (all the others were zipping around, chasing each other) Then it started going to the very bottom of the tank, falling on its side, but then getting up again. It didn't eat. Then slowly, it got worse and worse. I went to the store and they told me to add stress coat, which I did, but yesterday it died
The others looked fine and were feeding happily & the fish store said it was probably just that one was getting picked on by the others so I bought 3 more.
Then today when I got home with the new little guys, another one was dead and there's another one hanging out at the back of the tank with its tail floating up
The dead ones looked fine...they were just dead!
Any ideas?

Isabella

OK, did you measure ammonia, nitrite, and nitrate AFTER you've added your fish? What happens oftentimes is that even though a tank is cycled, if you add many fish at once, ammonia and/or nitrite can suddenly go up and cause your fish either to get sick or die (which is why it's always good to stock a tank gradually, adding 1-2 fish at a time). If you measured the parameters regularly after you've added the fish, and they were all at 0, maybe you've simply bought sick fish - that happens a lot. Many fish are bought sick but the disease may not show itself for a while (which is why many people have quarantine tanks - so that they can keep newly-bought fish in it and observe the fish for any diseases first, and if none are apparent, the fish are then put into the main tank).

Besides, I think it's recommended to perform a larger water change after the cycle is done, like a 50% water change.

P.S. A pH of 8.0 - 8.2 is not soft, it's hard.

cosmic dust

yeah, I've been testing the water every day - ammonia & nitrite stayed at zero. I was going to only add 3 fish at a time, but the lady at the store said it was okay to add 6 1 inch fish since it was a 30 gallon tank.
I know you're right about the quarantine tank.....I'll set one up before I buy any more fish, but what's funny is that none of the fish in the store are sick. hmmm.

Isabella

As I've said, just because a fish is sick, doesn't necessarily mean it has to look sick at first. It may take a while for a disease to show. Fish at fish stores don't stay there long - probably not as long as it would take for a disease to show. If you bought it sick (only yet without symptoms), then the sudden change of environment could have caused the symptoms to speed up and the disease to come out. However, if you bought healthy fish - as I've said - maybe ammonia and/or nitrite rose suddenly in response to a lot of fish added at once. If this wasn't the case, maybe you didn't acclimatize the fish? Did you acclimatize the fish? If so, how did you do it? Lastly, keep performing regular weekly water changes (15-30% each time), and vacuum the gravel well with each water change.

cosmic dust

To acclimatize the fish, I took a bucket and put water from the tank into it and then floated the bag in that water (our house is at the same temperature as the tank (78F) so I thought that would acclimatize the fish to the temp without puting a dirty bag into the tank). Over the next hour or so, I took some water out of the fish bag and added some of the tank water into the bag. I did this 3 or 4 times and then netted the fish and put them into the tank.
Two more died over the weekend
What we're noticing is that a couple of the fish are getting bigger with swollen bellies & when we feed them, they chase the smaller ones off, if the smaller ones even try and feed, which some of them don't. The only way we can give them all a chance to feed is by feeding a lot of food to give them all a chance to get some, but of course that means the bigger ones are being over fed. I've kept a close eye on the nitrites and ammonia, still none.
One question, I have a biowheel filter and an air stone. Should I turn these off when I feed? - they make the flakes zoom around the surface - is that good or does it make it hard for the fish to get it?
Should I be medicating the tank?
Thanks

Butterfly

Most filters have a way to turn the water flow down some and turning the airstone off at feeding time might help the smaller fish catch their food before it's swept away. Won't hurt to try Just remember to turn the filter back up and the airstone back on after feeding
Carol

Isabella

Well, sounds like your water is well. Maybe, after all, you simply bought sick fish. Anyway, do the water changes with thorough gravel vac's. As for myself, when I feed my fish, I turn the filter off for a few minutes. I don't like when they have to chase food and fight over food ("who's gonna get that piece faster", lol).