Peppered corys are dying
I had 5 peppered corys and 4 platys in a 15 gallon tank for a few months now. I left for a business trip for a few days, and when I came back, I noticed one of the corys was not doing well. It was laying on its side, and I thought it was dead, but it was still breathing. I did a pwc, then went to bed. This morning, the little guy kicked the bucket. I also noticed another cory acting strange - it would hang out near the surface, which it never used to do. I left work and when I got home, it was dead. I just did another pwc, but I noticed another cory is swimming a lot near the surface.
My water params are 0,0,20. I have an amazon sword that has a rotting leaf - should I take that out? I'd like to save the other 3 corys, but I have no idea what to do. Any thoughts?
whats the temperature of your water? pH? what kind of filter do you have? how do you measure your water parameters?
Im am so sorry about your little corys:cry:
Continuing on the water parameter issue, are those numbers now, or when you came back (ammonia 0, nitrite 0, nitrate 20)?
And the pH is important. What is the tap water pH? And what was the tank pH when you came back, and now?
And yes, if a leaf is yellowing, remove it. Normally wouldn't matter, but best to remove the excess organics if something is wrong.
My temp is a steady 77. The PH from the tap is 8.4, and from the tank is 7.4. Unfortunately I did not measure the PH/Am/ite/ate before I did the water change. I have an Aquaclear 30 filter, and I'm using the API kit. I've looked closely at all of the corys, and I haven't noticed any growths or any physical defects. The only change I made was 3 weeks ago when I added an Amazon sword and 2 platys from my old 5 gallon tank. Anyways, this morning the one guy thats been swimming near the top since last night is still doing that. The good thing is that he appears to be swimming normally, unlike one of the ones that died (swim bladder disease?).
I give them shrimp pellets on a daily basis, and once a week I give them algae wafers. I do put some bloodworms in there from time to time, but I'm pretty sure my fat platys take them down before they reach the corys. Should I be varying the diet more?
My earlier thinking was that a shock in pH or nitrates can be very stressful even to causing death, and when a tank is left alone for a period these factors can change significantly; then doing a large water change changes them further, so another shock. And Corydoras, even though this is the more robust Peppered Cory, are still highly sensitive fish to fluctuating water parameters and conditions. The platys for example could easily survive changes that will harm corys.
Your pH difference of 1 whole degree from tap (8.4) to tank (7.4) should be explored. While 7.4 is better for the corys, if it fluctuates quickly between these two it is bound to take its toll. Tank water will naturally acidify over time due to the organics and carbonic acid produced. The amount depends upon other factors such as the hardness of the tap water, as high carbonate hardness (KH) acts as a pH buffer to resist changes. Do you know the hardness of your tap water? This you can ascertain from the water supply people, they may have a website with a water analysis, or they can tell you if you ask. Get the GH (general hardness) and KH (carbonate hardness) if possible.
On the foods, yes, a variety is always better to ensure the fish get their balanced nutrition. Sinking foods are needed for corys, and I rotate 4 different foods. Omega One is a high quality food and they make sinking foods in that line. I also use Nutrafin sinking tablets; interestingly this is clearly a favourite among corys and loaches for some reason. And one should always be a veggie base, algae/spirulina/kelp or something. Most of these also have fish or shrimp meal so the corys will eat it, but getting their vegetable matter helps with digestion.
Frozen worms and shrimp also work but not as a staple. Try raw veggies like yam, sweet potato, squash; some aquarists report corys eating these. Also as a treat. They are primarily carnivore.
I gave the kind folks at my town a call, and they said the water was soft, specifically <17ppm. The guy I talked to could not provide me with GH or KH. I'll do a better job tracking the PH and see how it varies throughout the next few weeks.
The only thing out of the ordinary the past week was that I went on a trip for 5 days. I own an Eheim feeder that I scheduled to drop flake food once a day, and im guessing the corys didnt get much. Could not eating for a few days weaken their immune system? I thought tropical fish could go a week easy without food.
You hardness tells us a lot; you have very soft water, 17ppm is about 1 dGH. I have the same here. Lucky us, in that we can easily keep soft water fish. But the pH is not buffered so it will fall as yours has done. It is interesting that your pH is so high (8.4) but there are causes for this that I am not going to get into, too technical. The main point is that in a fish tank the pH will lower, and a lot and quickly.
My pH runs around 6-6.4 and with weekly water changes of 50% (tap water here is 7 or 7.2) this remains stable. In your situation with that high a pH, I would do smaller water changes (volume) to keep more stability. When you do a water change, the pH will naturally rise in the tank with the influx of high-pH tap water. Then it will lower within 24 hours. You want to minimize this fluctuation, and that means change less water.
You must do weekly water changes or you could have real trouble. I would settle on changing 30% of the tank volume once a week, always on the same day each week if possible, and use a good water conditioner. Monitor the pH, check it before the wc and the day following to get an idea of the difference. A change of .2 to .4 or even .5 is not an issue.
Back to the corys. I'm not going to guess at the cause, as there is much to choose from with these fish. I wouldn't have thought five days could make the difference. It is more likely a combination of things.
Thanks for the input. My fish and I certainly appreciate it. I will follow your advice and see how it goes. I was changing my water on the same day each week, but recently the schedule has been thrown off a bit.
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