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i fail at keeping corys...

6K views 29 replies 10 participants last post by  fish monger 
#1 ·
When I first started keeping fish, corys were my first fish. I had bronze corys first, then, later, peppered corys. Since I didn't really know what I was doing back then, the bronzies weren't a huge success, although it's amazing they lived as long as they did considering how I treated them. The peppered corys were a HUGE success, even though, or perhaps because of, the appalling conditions they sometimes had to survive (multiple cycling tanks, filter disasters, overstocking, etc...)

Anyway, since I found this site and actually learnt how to look after fish properly, I have had NO LUCK with corys. A few years ago I bought a shoal of beautiful little Panda corys from a large aquarium store. They were in perfect health when I got them, but not long after I introduced them to my tank they began to shows signs of gill flukes. I treated them and thought they had recovered, but shortly afterwards they died of finrot and fungus. More recently, I bought a shoal of - again perfectly healthy-looking - peppered corys from my local pet store and EXACTLY THE SAME THING happened! :cry:

My tank is 15 gallons, with a gravel substrate, a heap of plants, and very gentle homemade filtration using an airstone and some filter wool. There are also two pieces of driftwood which I collected many years ago. Not surprisingly, since they aren't real bogwood they are starting to disintegrate after so long in the water, but they still provide a good anchorage for my Java Fern. The pH is acidic but not wildly so (when I put the indicator fluid in the phial the color is a slightly greenish yellow.) I can't afford a hardness test kit so I don't know the kH but it's probably quite soft, if the water is that acid. The tank's been set up for over 2 years and is thoroughly mature.

I can't understand what's wrong. The only thing I can think of is that the gravel is quite full of detritus and since corys are bottomfeeders maybe that's making them sick. I siphon off as much of the muck as I can every week, but I don't have a gravel vacuum so there's a limit to how clean I can actually make it. When you stir up a bit of the gravel heaps of detritus comes out.

I have kept other fish species in this tank without any trouble; for some reason I just seem to suck at keeping corys! I'd really appreciate it if anyone could give me an idea of why I can't seem to keep them alive. I miss corys :(
 
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#2 · (Edited)
Sorry for your loss. I know how atttached we can get to the little guys :-(

I'm sure others with more experence will come in and give you better advice than me, but here is my take. Corys are a scaleless fish, so water contaminants, copper, and above normal levels of thing like amonia REALLY get to them. Also, gravel can hurt their little barbles and once they wear them down, they don't grow back! Between that and the dirtiness of the gravel, you might consider changing out the substrate to sand (stay away from pfs as it's too corse! Not sure about play sand as I've never had it, but be warned that it takes FOREVER to clean). You can also make a homemade vacume using a Coke bottle and a piece of air tubing. Googing diy gravel vacume should bring up instructions on how to do it. ;-)

If you can't change out the substrate quite yet, you can do a bit of cleaning using a turkey baster. I got one from Dollar Tree and you would be surprised how handy it is!
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#3 ·
My odds of being right are slim to none but I added a piece of wood collected from a local lake a week before adding a pleco and new plants. For almost 4 months I chased imaginary water problems and parasites as my fish were glancing. I blamed the pleco and the plants. My wife reminded me about the driftwood 3 days ago so I removed the wood and have not seen glancing in 3 days for the fist time in 3 1/2 months. Knock on wood, no pun intended. Maybe your wild caught wood is the culprit.
 
#4 ·
How long after you bought your cories did they get sick? Sometimes "perfectly healthy" fish bought aren't perfectly healthy after all. Also, how many did you buy?
 
#12 · (Edited)
The first time I think I got three or four (the pandas); can't remember how many peppereds, but probably a similar number. I can't remember exactly how long it was before they started to seem ill, but not very long, probably only a few days?
It's worth noting that when I first got the pandas I was in the process of setting up a new tank (which wasn't yet cycled, so I'm sure that didn't help!) and at first they were kept in a much smaller (6 gallon) tank while I waited for the new tank to settle down. They only started to show signs of illness once I added them to the new tank. But the peppered corys were added much more recently when the tank was cycled, and they got sick too...
 
#5 ·
Sorry to hear you are having so many problems keeping corys. From the information given, I would think the issue is with the amount of nitrogen compounds (Ammonia or Nitrate) in your tank. Try taking it to a LFS to see if they will test Ammonia, Nitrate, pH and your hardness (KH and GH). It behooves a store to test your water for free. These other water characteristics are good to know but are likely not the problem because of the wide range of conditions that Corys can be kept.

The visible detritus is what I am keying on as the issue. When you do a water change, you need to remove the debris or you could have a build up of ammonia or nitrate. Ammonia is far more toxic and when it is present in a just a small amount it can stress a fish leaving it susceptible to disease or kill the fish in a short period of time. Nitrate will also stress and kill fish but it take much higher levels.

I think some people get stuck on the idea that they are doing a certain percent water change and do not think about what they are trying to accomplish with the water change. Ilook at it as...

Over a period of time, the amount of Nitrogen (ammonia and or nitrate) removed needs to be greater than or equal to the amount of Nitrogen introduced to the aquarium and the more frequent the water change the smaller the spike of Nitrogen compounds.
 
#13 ·
I have a pH test kit and regularly test the pH, although I don't have a kH or ammonia/nitrite/nitrate test kit. The pH seems to stay constant at a slightly acid pH. I did buy one of those dip-strips for testing ammonia etc. and although I know they're famously inaccurate, it showed zero of any of those toxins when I tested the water! I asked people on here about this and they thought it was possibly due to the large number of plants (and algae!) in my tank using up all the nitrate.

I definitely need to get a gravel vacuum, or make one, to clean properly.
 
#7 ·
Corys are portrayed as hearty fish in many circles and they are given the proper conditions. My experience has been that they are very sensitive to change in water parameters. After having very mixed results, I have discovered that doing a 50% water change right before adding them to the tank has worked like a charm.
 
#8 ·
I wil have to try that next time I get more! anything that helps is worth a try :-D
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#18 · (Edited)
It is possible for a aquariums bacteria levels to crash. Introduce large amounts of Nitrogen and then drastically reduce the Nitrogen inputs. Similar to the famous ecology example of the fox and rabbit populations being interdependent.

Some fish are more sensitive to ammonia then others. Cory barbels will fall off with ammonia present at some pretty low levels; varies by species.

I went 10+ years keeping fish before I was serious about water quality and changes. :) I have seen a lot of hurt and have seen many others do the same. Cleaning tanks frequently is definitely not the norm in the hobby.
 
#20 ·
To start, if your tank was setup for over two years but had not fish in it then it'll lose its cycle. It needs constant fish inside of it, or if it doesn't have constant fish it'll lose its cycle.

Spend $10 and get a gravel vac and do a 50% water change weekly for a month with the gravel vac (assuming you have no fish).

Also, while corrie are schooling fish, try getting 2 and then wait a month and get 2 more. Or you can get all all 6, but dose prime daily for a month to remove cycling issues.
 
#21 ·
there WERE fish in the tank, just not many. Actually I can't remember my stocking levels at the points when I've had corys, but the first lot, I think I just had a gourami (a leftover from before I really understood about suitable tank sizes. She died suddenly from stunting after a year.) The second lot of corys I tried, the peppereds, I had at a time when there was a group of about 10 - probably more - small shoaling fish in the tank (can't recall whether I still had a gourami at that point.) I would have thought that the latter nubmer of fish would be sufficient to maintain a cycle. The first lot of corys don't really count as the tank had only just been set up at that point was still cycling.

good advice about adding the fish slowly. I'd get a gravel vac except I know the heads of those things are quite large, and my tank is so planted up there's very little freely accessible gravel. Even just siphoning with a small tube, I cause quite a lot of disruption to the plants. Thinking of making one myself.

anyway, I won't be getting corys again for a long time because my tank is currently completely stocked, and it's a nice setup :)
 
#22 ·
I have had great luck with my Corie's. So much so that they bred in my tank. I have Eco-Complete substrate and though it isn't soft like sand, they seem to do quite will with it. Also, I agree with the water changes. It might be the secret to my success with them. I recommend a 75% water change weekly if not every 5 days. Clean water is the key. Yes, get yourself a gravel vac as it not only makes the cleaning easy (so you are more likely to do it) but I think on occasion one needs to get a bit of the filth from the gravel.

I do not recommend only getting 2 at a time. I would recommend that normally when adding fish but with Corie's, I would get a minimum of 3 of the same species and then if you wish for more, add another 3 of the same or compatible species. Also, adding several live plants helps too. Cories do seem to hang out under my large Amazon Swords the most.
 
#23 ·
my tank is completely overgrown with live plants :-D
If only I had the room - and the money - for it (and thought my mum would let me) I'd set up my other 15 gallon tank which has used as a table for years now! It would be so great to have 2 relatively large tanks to work with. Then I could have corys again.
 
#24 ·
Admittedly, I wouldn't keep Cories in a 15 gallon tank. They are incredibly active little fish. They are all over my 60 gallon like popcorn. They are up, down and all over the place. Hyper active little guys. Then all of a sudden you look and they are all laying on the bottom right next to each other, sleeping. Very cute.
 
#25 ·
I don't have the room for a larger tank, let alone the money :-( How many corys do you have? I know that they're shoaling fish, but the happiest corys I've ever had I kept as a pair. most of their life was spent in a 6 gallon tank, which I admit is much too small, but I didn't know that back then! :oops:

by the way, did you get the 'wet' eco-complete that's like soaked in bacteria-infested water? would you reccomend it? what does that do to cycling the tank?
 
#26 ·
I have Eco complete in all of my tanks without issues. In my larger tank I have about 18 Cories and in the 30 gallon I had 6. They really are very active and I believe that the consistant water changes is the key to keeping them healthy.

Not having money or room for a larger tank is not an issue, you just need to pick fish that best work with the situation you have. Sounds like your tank is full now anyhow so you will be good for a few years. Merry Christmas! :)
 
#28 ·
Yes, you can keep a group of 5 to 6 Cories in a 60 litter tank. I prefer sand as a substrate for them but you can use small gravel that is rounded. I have experienced issues with rounded gravel and Skunk Cories. Their barbels have been thinning while the other Cory species have not had issues.
 
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