Die-Off

[Autonerd]

Hi all -- A follow up to a post in Tropical Discussion (http/www.fishforums.net/index.php?/topic/433643-disappearing-fish/)
 
I mentioned that I was trying to restock my 2-year-old tank, adding more Neons and Dwarf Corys. Most of the new fish I've added have disappeared. (I suspected a ghost shrimp who has since died, but fish are still disappearing.)
 
In the last 48 hrs, two of my three mature Neons have died, and one of the corys is showing signs of distress (though he's done this before). (UPDATE: He's back to normal now.) Tested the water and found that pH has risen to 8.0. Tap water is testing at its usual 7.4. Other parameters are testing as usual, though ammonia has gone up from 0 since I started adding fish and nitrates are a little high (a constant battle). Water parameters below.
 
I have been doing 2.5 gallon changes every two days. Today I did a 50% change. 
 
In the original thread, Fish Herder asked about filtration -- I use an AquaClear 30 filter. I rarely change the media, though I occasionally give one component at a time a light rinse.
 
Tank size: 15 gal
pH: 8.0
ammonia: 0.25
nitrite: 0
nitrate: 40 
kH: Don't know
gH: Don't know
tank temp: 80F

Fish Symptoms (include full description including lesion, color, location, fish behavior):
Two mature neon tetras dead, found near filter intake, blue sections of body gone white.
One mature dwarf cory on side at bottom of tank, gills moving, color OK. He's done this before. (UPDATE: He's back to normal, in the time it took me to write this.)
Volume and Frequency of water changes:
Varies, recently 2.5 gal 1-2 times/week

Chemical Additives or Media in your tank:
NovAqua Water Conditioner Plus with new water
Tank inhabitants:
2x Neon Tetras (1 mature, 1 new -- 2 mature just died), 2x dwarf corys (mature), 3x assasin snails, some MTSs

Recent additions to your tank (living or decoration):
4x neon tetras (three died), 3x dwarf corys (all disappeared), 3 small plants

Exposure to chemicals:
None that I know of
 
 
Thank you for your help!

 

[Meeresstille]

First, sorry that you are having such a hard time with your tank and fish dying. There are 3 things that stand out for me:
 
1) I think your weekly water changes of 2.5 gallon in a 15 gallon is not big enough, even if done twice a week. I would change 50 % every week (7.5 gallon) in a 15 gallon tank, but looking at your pH issue doing multiple smaller changes would be more sensible. If this were my tank I would change 3.5 - 4 gallons twice a week. It would help bring those nitrate down while keeping your pH from fluctuating too much. (do you have nitrate in your tap water as well?) Once the tank's water is closer to your tap water's pH you can then go to doing 50% water changes.
 
2) The pH having gone up in your tank: have you tested your tap water's pH after letting it sit for 24 hours in a glass? If it is staying at 7.4 after 24 hours then there is something in your tank that is raising it. Any unusual rocks, or decor that may be the culprit? A fluctuating pH can cause fish deaths, and a sudden change of .5 can bring death on quite quickly in sensitive fish.
 
3) Quarantining new fish before adding them to your main tank. If you quarantine your new fish for 6 weeks you can observe them for any problems and should there be any you don't have to treat your main tank (which saves money on products and meds) and you don't run the risk of your older fish dying from diseases the new fish have brought with them.
 
Also, ammonia in your tank being .25 could be from having added the new fish and the bacteria trying to catch up with the higher bio-load, but at a pH of 8 you need to do water changes to bring those levels down. At a pH of 8 there is a lot more ammonia in its toxic form than in a tank with low pH. If your water conditioner states it makes ammonia safe then this will only be good for 24 - 48 hours at which point the ammonia will return to its toxic form. (do you have ammonia in your tap water? is your city treating the water with chloramine?)

 

[bluesword23516]

The neons do lose the blue when they die, it is just how it works. Have you noticed any red gills or white spots on the fish when you find them? Or just anything that wouldn't seem normal for a healthy fish? 

 

[Autonerd]

Meeresstile, thanks for the info -- I have only tested immediate pH on my tap water, I will try 24 hrs and nitrate tests. Unfortunately I don't have a setup for a quarantine tank -- the last time I added creatures (besides ghost shrimp and the assassins) the tank was freshly cycled, so it *was* the quarantine tank. (And at the rate I'm going, I could be starting over!) I will try the alternate water change schedule you suggested, lots of small changes.
 
Bluesword -- Thanks also. I did not notice this on the fish, but I didn't look very closely.
 
If I can save the fish I have, I'll have two of each. Recommendations on restocking? Should I look at adding one fish at a time?
 
Thank you!
Aaron

Quick update: The cory who was showing signs of distress died during the day. There seemed to be a faint metallic pink behind his gills, not angry red.  I didn't see the other cory, but I have chemicals on my hands and didn't want to touch anything in the tank. Two neons (one mature, one new) are okay, no coloring on or around gills that I can see. Haven't tested the water yet.
 
Aaron

 

[Meeresstille]

Oh no, that cory died too? I think it is some kind of toxin that is killing all your fish. Although your nitrates are a little high, I am not convinced that these are at fault, but it would be best to get those levels down to between 10 and 20 before you start adding any more fish. 
 
When adding fish to an existing tank go slowly, I would add no more than 2 fish at a time to a 15 gallon tank to prevent any major ammonia spikes.
 
The pH too needs to get straightened out. And do you know what the LFS' tank's pH levels are?
 
There is no possibility that any cleaning solvent has gotten in your tank, is there? Have you recently painted something that may be emitting fumes near your tank? Any new furniture or new carpet? How old is your fish food? 
 
I know how sad and frustrated you must feel, my son has gone through something similar recently trying to set up an 8.5 gallon Betta tank. One after the other they all died within days of being added to the tank (which was cycled). They all seemed to have different symptoms and it took us a while to figure out that there must be some kind of toxin in the tank. We have gone through the process of elimination, from getting a new tank, to slowly adding things back to the tank like substrate, plants...we are using some shrimp as "tester fish". In my son's case it may have been the rotting palm tree root of a dead potted palm tree that had been left sitting in the corner of their living room. Apparently they emit some toxic gas when they rot! 
 
It may take some time for you to figure out what it is that is killing your fish, that's why you need to get all the parameters that are a little off straightened out. Once that is all clear you can then start adding new fish.