Losing cories and not discus

[Latro]

When I started this tank, that is towards the end of its cycle, I put three cories in it. One of those died pretty quickly (over a period of days), although he was something of a loner and a runt, so that didn't surprise me all that much. After that I got two more cories of a different type, and over time the remaining two of the original cories also died. Now today one of the newer cories died. What could I be doing that might kill cories and not discus? (The obvious answer is "not feeding the cories food they can get", which I'm not doing, so what else?)

[moon_knight1971]

Have you tested your water? What are you using to treat your water to make it fish-safe? Are you quarantining the fis before you place them in the tank? Also, what temp is your tank? If memory serves only 3 types of Cory are actually from the same waters as the discus so they can handle the higher temps dicus need.

[Keith Perkins]

Is it possible you have a discus that likes to pick on cories? Some certainly like tetras and other community fish, and not necessarily from the get go. Some as they approach or enter spawning age develop the like. Any signs the fish have been picked at?

[Latro]

My discus seem to completely ignore my cories; they may be swimming right past and not even seem to notice them. I wasn't quarantining these fish at the time, but all of the deaths were sudden and after an extended period (several weeks other than that first exception). The bodies didn't appear to have been picked at, either.

I use tap water with some salt and Prime. I'll get recent parameters later today. Temperature is between 83 and 84 F (that's the main thing that's radically different from a well-taken-care-of community tank, so it was my first guess).

The first group were corydoras arcuatas; the second group is corydoras panda.

I have a large gravel substrate (that is the individual rocks are pretty large), could that be part of the problem?

[moon_knight1971]

Do the dead Corys look bloated? They can eat too much and kill themselves for over doing it.

[Latro]

They're tiny little things, so it's kinda hard to tell, but I could actually see that being the case. And these guys had a feast a couple days ago, too, because I put half a beefheart cube in without breaking it up (not doing that again; only one of my discus found it, and it sank to the bottom very quickly) and they were chowing down on it pretty greedily.

[discolicious]

Cories are generally listed as preferring temps between 71 and 79 degrees. They tend to be fairly tolerant, so I would be surprised if the temperature alone caused them to die. Generally, their death (in a discus tank) is due to the fact that discus are bottom feeders too and have the ability to blow up the food from the gravel and get it before the catfish do. If you've been specifically feeding the catfish in a way that the discus can't get to the food, then I would reluctantly guess the temp. If your substrate is rough edged gravel, it can damage the barbels of the Cories, which they use to find food... just a thought.

[moon_knight1971]

They're tiny little things, so it's kinda hard to tell, but I could actually see that being the case. And these guys had a feast a couple days ago, too, because I put half a beefheart cube in without breaking it up (not doing that again; only one of my discus found it, and it sank to the bottom very quickly) and they were chowing down on it pretty greedily.

Think it's the beefheart then. Pretty sure Corys have issues breaking down that much beef heart

[Latro]

Cories are generally listed as preferring temps between 71 and 79 degrees. They tend to be fairly tolerant, so I would be surprised if the temperature alone caused them to die. Generally, their death (in a discus tank) is due to the fact that discus are bottom feeders too and have the ability to blow up the food from the gravel and get it before the catfish do. If you've been specifically feeding the catfish in a way that the discus can't get to the food, then I would reluctantly guess the temp. If your substrate is rough edged gravel, it can damage the barbels of the Cories, which they use to find food... just a thought.
They can generally compete with my discus for small amounts of their usual food, especially the flake food, and the discus are generally not interested in the shrimp pellets that I feed specifically for the cories. The gravel doesn't have rough edges as far as I can tell, though; the rocks are fairly large but smooth.

Think it's the beefheart then. Pretty sure Corys have issues breaking down that much beef heart
Good to know; wish I had known before I lost these guys. I guess the best solution is improving vacuuming habits a little (that is, doing some surface vacuuming daily, without the scale of a full WC (which I do every 2 days or so)) and feeding my beefheart in more pieces (so the discus can get more of it before it sinks, at which point they are still interested but less so).

If I get a +1 on cories struggling with beefheart I think I can safely call this case closed (and more importantly fixable). By the way, what are these good varieties of cories for high temp tanks?

[Jhhnn]

I don't keep cories- just discus, but I know that cories don't do well at higher temps, whereas discus do just fine. Be sure that your thermometer is accurate & hold temps towards the lower end for discus, 82-84F. Sterbai cories are supposedly better at high temps than most...

Hopefully somebody with solid experience will chime in...

[Scribbles]

I used to have cardinal tetras and at one time a couple of plecos. The discus didn't bother them during the day but early one morning I discovered the discus picking on and killing the other fish while they were still sleeping (tetras). It explained all of the losses of apparantly healthy fish. They just gang banged the poor pleco.

Chris

[discuspaul]

I've had good long term experiences with keeping Sterbai, Bronze, Emerald, and Pepper Cories with Discus @ 84 to 86 F temps.
Not so with Pandas however - they don't seem to manage the high temps nearly as well.

[CajunAg]

I've had good long term experiences with keeping Sterbai, Bronze, Emerald, and Pepper Cories with Discus @ 84 to 86 F temps.
Not so with Pandas however - they don't seem to manage the high temps nearly as well.

I'm also keeping Sterbais between 84 and 86, seem to be doing just fine...

[stephcps]

+1 for sterbais and bronze. I have heard the same about the pandas nortoriously not handling the high temps. My vote is for temp as the reason they died.