What? Why?

[Gibberwatt]

I have two tanks:
A 29 gallon, with two angels, a Red-tailed shark, and 7 cories.
A 15 gallon, with one angel, 4 black neon tetras, a blue neon, and some lemon tetras.
Don't comment on the angel/tank size problem. I already know about that.

Last Sunday, I forgot to do the weekly water change (getting home from vacation). I decided that since my tanks were fine, I would wait until this Sunday (Today)

Yesterday, I noticed one of the black neons with dropsy, which is a bad water disease, I think. Today, I found that instead of having 7 cories, I had 4. One died this morning. And I would have noticed a corpse floating around, so the other two must have died some time during my vacation (from the 21st to the 28th). Why have my cories suddenly died? They've been fine for months.



Again, Please don't comment on the tanks being to small for the angels, unless directly related to this problem. I know about that already.

 

[Autumnsky]

What are your test results/ tank parameters? Ammonia, Nitrite and Nitrate? Liquid or strip test?

Do you know if your tank is cycled? When was it completed and for how long?

What is your temp?

Was someone feeding while you were gone? Did they feed too much?

When you have too many fish in a space or over feed or don't do a needed pwc your parameters tend to get out of wack and then your fish take that stress and it weakens their system and they get sick.

How do you know things were fine when you got home from vacation?

Suggest a water test. At least save a cup of water from each tank to take a sample in to be tested after you get done with your pwc.

That being said you would probably be wise to do 2 - 50% pwc back to back. The reason it is 2 is to keep the water changes more gradual. Then test again and compare the differences. Do not put the filter pad in untreated water because that will kill your BB, just rinse in pwc tank water and if you need cleaner water to rinse just use fresh treated water.

 

[coralbandit]

The angels and red tail could be aggressive towards the cories?
How much water do you usually change?
Do you know what your nitrAte reading is?
Dropsy is more a symptom then true disease, usually resulting from water conditions there is unfortunately more to it that we just don't have nailed down.
Unfortunately by the time a keeper notices the swelling tremendous internal damage has been done and odds of recovery are low.
Look into EPSOM salt as often constipation can be confused with dropsy and can also help relieve the bloating due to fluid retention.
The fluid retention is improper osmoregulation and is doing damage to the fishes organs.
Good luck and change a little more water then usual today.

 

[Gibberwatt]

The 29 has been cycled for upwards of three years, the 15 less than 2. I've already rinsed the pads in the 15, I will do it in the 29 right now.
And I have noticed the shark chasing them around, but they just go under a log, or through a mat of plants, and he looses them.
I change 30% weekly in the 15, and 15% weekly in the 29 (the 29 is heavily planted)
I have no Idea what the readings are, since I don't really check them. Whenever I do, I get really low readings. The temp is 76 in the 29 and the 15.


I did get someone to feed my fish. They have never had fish, though, so that might be my problem. After I finish summer school (BOO) I will give the tanks a complete/total cleaning.

Thanks for the help.