dying cory cats

[ravekiss]

I dont have live plants that can cause residue and my temp is at around 78 and I have the same problem with the corys dying...I cant seem to find out why and its very sad because I love corys.

 

[OohFeeshy]

six green corries

Green?

 

[jaimoe]

I think it is  most unlikely that plant residues are the cause. When plant material breaks down, the visible "gunk" is mostly lignin and cellulose which although unsightly, is not particulaly toxic.

Something which raised my eyebrow when I read it is that you keep the tank at 80, that seems quite high to me. The warmer the water the lower it's Oxygen holding capability. Why do you have it that high?

Another issue with Corys is food. Do you feed a sinking food for them? I have found people who "can't keep Corys" were, in fact, simply starving them because they assumed there was enough flake or whatever getting down to them.

My girlfriend is the one who originally started this thread, so I'll give an update on what's been going on.

The water is at 80 degrees because that's as low as we can keep it in the heat of the summer. During the winter we keep it at about 76-78 degrees. The problems started before the weather got warm though. And yes, we did feed them sinking pellets. We had two kinds, one made specifically for catfish with shrimp in it and some green algae pellets that we also use for our cichlids as treats.

Like my gf said, we lost the last cory recently, so now we have none. All of the tiger barbs and the blue dwarf gouramis are doing well though. I THINK I might know what the problem is though. When we originally started the tank we bought a very small filter that we thought would be big enough until we could replace it. We never replaced the filter though and on top of that the
gunk from the dying plants slowed the filter down condiderably. Even after cleaning out all of the dead plant matter, I still don't think it is at 100%. Perhaps the cories are a little bit more vulnerable to those types of conditions than the other fish? We're going to leave the tank alone for a couple of weeks and buy a larger filter before putting any more cories in this tank. Hopefully this will solve the problem. If not, I don't know I guess we'll just have to give up on cories! At some point I can't justify buying any more if they are all just going to die on us!

Either my gf or myself will keep this thread updated as things develop.

Oh and BTW the green cories I think are more commonly known as bronze cories. They are the common brown ones you can find anywhere. I think they're called green cories because in the right light there is a greenish sheen to them.

 

[OohFeeshy]

Ah right, I was thinking 'its not likely to be the gorgeous green lazers as their worth their weight in gold, they're not the dyed albinos are they as that would explain a lot'. But I've never heard bronze's called green

 

[TheLoveDoctor]

Your Zebra Danios are slowly picking them apart!! I guarantee it...
Muy Zebra Danios killed 1 of my Cory Cats and then killed all of my Cardinal Tetras… 
 
Another thing! Temperature is too hot. Lower it too 78 degrees or 77… 
You can put a fan on it to cool it down at least 1 degrees, maybe even 2 degrees. 
You an also put a cold or frozen/ cool bottle in there for a while to cool it down...
 
You also need to lower the PH a little.. I keep mine at 6.5 to 6.8 and they are extremely healthy… and Happy!
 
When your Ph is at 6.5 to 6.8, the Danios will not be so aggressive… 7.0 will be ok too but that's max high Ph… 
High ph makes some fish aggressive. Another thing is Zebra Danios can also become aggressive if they do not have 
enough of them in a pack. I think you said you had 4. That's not enough...
 
Personally I took out my Zebra Danio's and I have never had a problem since… 
 
And you really should have zero ammonia, nitrites and nitrates… 
 
use a Product called Special Blend Microbe lift. It's a all natural bacteria that will eat up waste and food at the bottom
so you don't have to do as many water changes.. and it keeps your water very healthy for the fish… 
 
I also use 2 products by Seachem to lower the ph and still build a stable base so it, the PH, won't drop or shoot up!
 
Use both Seachems products, Discuss Buffer 5.8 - 6.8 with Neutral Regulator 7.0. this will slowly lower the ph over time to 6.5 to 6.8. When you first start a tank, you put in a little tiny spoon of each once a day for a month, But it depends on your tap waters PH level, which I recommend because it has the proper minerals to stabilize the PH… RO Water and Rain Water does not have this and can cause quick drops in PH or vise versa which can kill your fish.
 
And, you can't use this product with Acid based Ph buffers… so if you are not using those, you will be fine and if you are using gravel or inert sand etc.
 
The other thing, is the Neutral Regulator 7.0 also takes out the Chlormine, Chlorine and Ammonia, so this is now your tap waters conditioner. And it slowly lowers ph over time… So since your tank is already going, just test the PH and also the Nitrates, Nitrites and Ammonia every few days to see where they are at. They should all be at zero. When it gets to Zero and the PH is around 6.5 to 6.8, you can stop using these products. Then only use them both together when you do a water change. use them and they will also be the water conditioner for the chlorine and chlorinate and ammonia out of your tap water… 
 
Also the Bacteria Microbe lift I recommended should be used every day for a month, when starting a new tank. So with your tank if it already has bacteria in it, I would say put in a capful, if your tank is about 20 to 30 gallons, 1 time at night for about 1 to 2 weeks. And the bacteria should really make your tank very healthy… Then just add a capful 1 time with each water change.
 
If you add fish, then add the bacteria again for 3 days.

P.s. when you use the Seachem Products, you use the tiny, tiny spoon it comes with!! Not a teaspoon, that is way too big!
 
And take a cup and put the Seachem powders in their and use the water directly from the tank.. let it blend and dissolve for 
a minute or to… and slowly add it or use a drip system or simply slowly put it into the water filter and let it go through there… 
 
You can just drop the powder into the tank but it could shock the fish a little. It's never hurt my fish… But at least mix it  with some of the tank water in a cup of some kind for a few minutes til it dissolves. Then slowly pour some in the tank, ie. 20 seconds or so. That would be good enough… 
 
P.s.s. the Neutrual regulator when used long enough will create a good base so the ph will be more stable and will only shift slowly over time, not in a big drop, etc. 
 
Again, this is a phosphate based product and should not be used with the acid types which you really have to be careful with. 
You can Call Seachem and ask them more if you need… or talk to a Fish store rep who has had a lot of experience with fish and knows what they are talking about..