Cory Cats Dying?
I have a 55 gallon tank with Angelfish, Cardinal Tetra, Cory Cats and an Emperor Pleco. The tank has been up and running for almost two years now, the water tests fine and I do a 50% water change weekly. I have done a couple of different stocking schemes with it but I am very happy with my current setup. The tank has smooth gravel, lots of driftwood and is fairly heavily planted. I have never had issues with fish dying and am stumped by this one. I have had 6 leopard cory cats for about a month now. Over the past few weeks I have slowly been picking them out of tank, and today I removed the last fallen soldier. They were very active for the first week or so, as expected, and then they just started laying around doing nothing. I make sure food reaches the bottom for them and they seem to be eating. What is totally blowing my mind is the Angelfish and Cardinal Tetra are completely fine and I would think they would have health problems long before the cories, but I have not lost any of them. I need to figure this out because the cories complete the biotype and I really like the activity of healthy cory cats. Also, my plan now is to do Sterbai and they are running about $10 a fish in my area.
Whats the hardness and ph of your tank? I have had some bad luck with cories, some live and some die for no apparent reason.
pH is 6.8 I, I assume the water is soft considering the pH.
This is not that uncommon, but there is always a reason so let us work to help you find it.
Can you test and post results for ammonia, nitrite and nitrate?
Live plants? And some wood (real or artificial) on the substrate?
Water hardness for tap, you can find this out from your water supply people; I agree it is likely soft/medium hard, but let's check so we can eliminate or deal with it.
Which water conditioner?
What food reached the bottom, just flakes or actual sinking foods?
How large is the pleco?
0, 0 , >10
Amazon Swords, Anubias, Valisenria, driftwood, average aquarium gravel
I use Prime with water changes and Flourish comprehensive weekly. My pleco is about 6 inches (largest fish in the tank), could he be messing with the cories? I would prefer to have a large school of cories rather than one pleco. I use mostly flakes, but I feed sinking pellets every other day.
Temperature is 80
Those I have kept at temp's much above 75 degree's F, seldom lasted longer than a few month's to a year with exception of Sterbai corydora's.
I believe they would benefit from shrimp pellet's, blood worms,chopped earth worm's,spirulina pellet's,bit's of krill,all offered after light's off for the evening.
Much bacterial activity takes place on substrate and in my view,this could result in low oxygen level at substrate where these fishes spend their majority but this is only my feeling.
Could also be that bacterial activity (decomposing organic's) make these little fish more susceptible to bacterial infection's but It is speculation on my part.
Creating some movement along the substrate by use of powerhead or positioning spray bar differently may help.
I personally quit keeping these cory's (False Julii ?) for I too was having problem's with them dying despite what I felt was proper care after only a few month's.
Wish I could help more.
Did note that the ones I lost ,,their Barbel's slowly deteriorated before succumbing, and it seemed to make no difference whether they were moved to sand substrate, or left in tank with smooth gravel.
Aside from the temperature, I don't see anything of concern in your numbers and responses to my earlier questions.
Corys are sensitive fish. When something goes wrong in one of my tanks that has corys, they are without question the first fish to show it. Example, when I had a problem with fungus from Mopani wood, it was the change in behaviour by the corys that alerted me; I know of others who had corys die from this fungus but not other fish. When the canister on my 115g got a bit clogged, it was the sudden change in behaviour by the corys that caused me to notice it. The point here is that they must be acclimated carefully, but also they suffer a great deal by collection, transport, poor conditions in the store--and all this takes a toll. They are highly sensitive to ammonia and dissolved waste, and here I'm thinking of their transport to the store and perhaps home to you. It only takes a very minimal level of ammonia to seriously affect any fish, and the damage may not become obvious [i.e., by death] for some time.
On the temperature, assuming you have tank-raised angels and not wild caught, you should lower your temperature to 77-78F. Wild angelfish need warmth, but not tank-raised. Higher temperatures quicken the metabolic rate of all fish, requiring more oxygen, higher respiration--in short, the fish is working overtime the higher the temperature is, and this means a shorter lifespan. Always maintain fish at the lower end of their temp range, or as low as possible when considering all fish species in the aquarium. I have found 77-78F (25C) to be suitable for the majority of tropicals. Some require higher and need that--discus, wild angels, some gourami. But most manage fine at 77-78F. A couple degrees may not seem like much, but to a fish that is dependent upon the temperature for all its internal functioning, it can be significant.
So I guess I will start by lowering the temperature gradually, but I have more questions. Are there species of Cory Cats that are hardier than others? Is there one that you would recommend? I don't care for the Bronze Cory Cat which seems to be the most abundant. Also, when cleaning the tank, I am a little confused. I had read not to siphon the gravel because of the plants, but how do I remove the collected fish waste and decomposing food?
To the substrate. You shouldn't be seeing waste and excess food; the latter means too much feeding. I have fine gravel and sand substrates and unless I deliberately poke into it I don't "see" anything. The waste gets pulled into the substrate where it is broken down by snails and bacteria.
I sometimes think people expect the substrate to be sparkling clean, but that is unrealistic. I may have as much stuff on mine as you do--if I take a magnifying glass I can see it;-), so it could be our individual perceptions? Just a thought. This is where a video would help.
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