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I am in desperate need of help. Since 9/28/2010 I have lost 11 cory aeneus catfish. Only my albino and green corys have been dying. I also have 7 sterbai corys. I have not found any of these dead, and I do believe most of them to be alive. 10/3/2010 was my worst day, I lost 5 fish in one day. 10/4/2010 I lost one fish and nothing on 10/5/2010. As of this morning, 10/6/2010, everyone seemed alive and okay. But every cory that died has looked and acted healthy. I added the new sterbai corys on 9/16. They were all alive and healthy. The deaths of my albino and green corys started 12 days later, on 9/28/2010. Did my sterbai corys give something to my other corys?? I don't know. I have included all relevant background information. Your help is very much needed. I can't solve this on my own.

1. Water parameters
a) Temperature range. 76.6 (night without lights) -77.1 F
b) pH. 6.6-6.8 Usually 6.8
c) GH. 4-5
d) KH 3-4
e)Ammonia=0, Nitrate=15-20, Nitrite=0, levels.
*Nitrate levels were always low until 9/11/2010. That is my first recorded higher level. It was recorded as 30 ppm. I was bad and didn't check the nitrates from 7/16 until 9/11.
I will note that I used to have many different types of shrimp in my tank. On 6/11 I had a massive shrimp die off. I lost every shrimp I had. I still don't know what happened. Maybe this is related?
f) Water change frequency
I do not have a schedule. I work horrible hours and don't have a set schedule. I will go back one month and give you my water changes.
9/2 20%
9/11 20%
9/16 15%
9/21 15%
9/28 20%
9/30 15%
10/1 50%
10/3 60%

(Most LFS's will check your water and give a list of readings).

2. Tank set up
a) Size. 65 gal planted tank
b) Substrate. flourite and play sand
c) Filtration. HOB marineland filter, 350 marineland canister filter
d) Furnishings. Various plants, driftwood (placed in tank many months ago) Slate
e) Other tank mates. Neon tetra=4, rummynose tetra=1, balloon mollys=5, baby ballon mollys=6, Big molly=1, guppy=3, guppy baby=?5, butterfly pleco, sterbai corys=7, albino cory=?, green cory=6,beta=1, platy=1, platy baby=3 (shrimp =0, everyone died around 6/11. My birthday of all days.)
f) How long has it been set-up? 2.5 to 3 years

3. Symptoms / Problem description
Sudden cory deaths. Started on 9/28 and about everyday 1 to 2 have died. On 10/3 I had 5 deaths. I had done a 50% water change the day before. I did a 60% water change after I found the 5 dead corys. I have only had one death since the 60% water change on 10/3.
Corys act normally. They eat, they swim, they are fast and I can't catch them. Their barbells are normal. Some are even fat.
My last death, I cut open. The cory appeared to have increased redness on her side. It was if, she had massive internal bleeding. When I opened her up, her intestines smells very badly. I have dissected fish before, and it seems like this fish smelled worse than usual.

Here is all the data I have...
9/19-15% water change, dose my ferts (KNO3 2gm, KH2PO4 0.3gm, K2SO4=7gm, CSM+B= 0.4gm)
9/21- 20% water change. No deaths, everyone is fine
9/28 - FIRST DEATH!! 20% water change, dose ferts (KNO3 1gm, KH2PO4 0.3gm, K2SO4=7gm, CSM+B= 0.4gm)
9/29 -SECOND DEATH
9/30-THIRD DEATH, Levels checked....results as follows
ph 6.8, Ammonia 0, Nitrite 0, Nitrate 40!!!!!!!, Phoshate 2.1 !!!!
On 9/30 I did a 15% water change, spent $17 and battled bad traffic in town to get API nitrozorb, Nitrosorb inline at 8pm on 9/30
10/1 TODAY- 2 Catfish dead!!!!! Levels checked at 9am
ph about 6.7, ammonia 0, nitrite 0, nitrate 40!!!!, phosphate 2!!! Temp is 79.5
10/3 ph 6.8, nitrate 20, temp 79.7, 60% water change --> 5 deaths
10/4-one bucket of RO water added, 1 death at night
10/5 ph 6.8, kh 3-4, gh 4-5, ammonia 0, nitrite 0, nitrate 15-20, phosphate 1, temp 76.6 (lights off, temp was lowered on 10/3)- NO deaths, one capful of excel
4. Action taken water changes, lowered temp from 79 to 77, STOPPED FERTS

5. Medications used NO MEDS USED, just stress coat for water changes

So, to start with, I'd say that 40 ppm is not lethal to most corys, and not to the common (albino corys are nearly certain the same species, there are some other species that are also albino, but they are much less common), and as I have kept for several months in local tap-water that is about 35ppm to start with and accidentally gone over 100 ppm for a short time, I'm pretty sure these tolerate a lot higher nitrate levels.

However, I don't really see the point in adding Nitrazorb _AND_ adding KNO3 to the water - that's a bit like putting your clothes in the dryer, and then hanging them in the shower to get them wet again! Obviously, your tank is, in some way, generating more nitrate than your plants are taking up. Similarly, you are adding phosphate to the tank, then writing "Phosphate 2.1!!!!" as if this is some kind of surprise... Phosphate isn't particularly harmful to fish, but if not ablace

The fish in the picture shows no apparent signs of illness, but they do look quite "fat" (round belly) - is this the case also for the ones that are still alive?

So, my conclusion is that there is something else that has changed. Perhaps there is something in your tap-water [which makes it difficult to fix], or you have changed your type of food, washing your hands with different soap, using a different cleaner, spray from insecticide, or some such.

--
Mats

Mats,
Thank you for telling me about the nitrazorb. I didn't realize it was going to take my KNO3 out. Some of my other catfish have fat bellys like this one did. Not all of the ones that died were fat. This one just happened to be a bit round. I just thought she was a female.
No new food. I am really good about washing my hands before I go in my tank. I rinse well, so I don't think it's that.
I have read articles about Hexamita, but I contacted the author. I actually spoke with Dr. Harrison and he doesn't think my situation involves the Hexamita. He actually thought it was a water quality issue. How much water is everyone changing on this forum? And how often??

Thanks
Cary

MatsP wrote:So, to start with, I'd say that 40 ppm is not lethal to most corys, and not to the common

Corydoras aeneus

(albino corys are nearly certain the same species, there are some other species that are also albino, but they are much less common), and as I have kept

Corydoras sterbai

for several months in local tap-water that is about 35ppm to start with and accidentally gone over 100 ppm for a short time, I'm pretty sure these tolerate a lot higher nitrate levels.

However, I don't really see the point in adding Nitrazorb _AND_ adding KNO3 to the water - that's a bit like putting your clothes in the dryer, and then hanging them in the shower to get them wet again! Obviously, your tank is, in some way, generating more nitrate than your plants are taking up. Similarly, you are adding phosphate to the tank, then writing "Phosphate 2.1!!!!" as if this is some kind of surprise... Phosphate isn't particularly harmful to fish, but if not ablace

The fish in the picture shows no apparent signs of illness, but they do look quite "fat" (round belly) - is this the case also for the ones that are still alive?

So, my conclusion is that there is something else that has changed. Perhaps there is something in your tap-water [which makes it difficult to fix], or you have changed your type of food, washing your hands with different soap, using a different cleaner, spray from insecticide, or some such.

--
Mats

I have no idea who Dr. Harrison is, so not sure if that's a good or a bad thing.

Water quality, at least in the sense of the measured values, appear to be correct in your tank. But of course, there are all manner of other things that can be counted as "water quality". It's been known that water companies accidentally get pesticides for example in the tap-water. I'm not saying that is the case here, just saying that it has been known to happen.


Yes, it may be that your fish is a gravid female - in fact quite likely.

I change about 50% each week on my tanks. Big/frequent water changes is never a problem as long as:
1. The new water is dechlorinated.
2. The old water and the new water have similar parameters (pH, hardness, temperature, etc).
3. The new water is "good", in that it is "better" than what is already in the tank.

The size of the water change should really be a function of the amount of fish you keep in the tank.

--
Mats

When you do your water changes, do you use tap water? Is Reverse osmosis water better? If I use RO water, do I have to add minerals??
Thanks,
Cary

At the moment, I'm using tap-water, as I've recently moved and the RO unit is not running yet.

RO water is only better if there is something in the water that you need to remove - in my case, nitrate.

And yes, RO water requires minerals if you want stable pH.

--
Mats