panda_luver

Well, I bought a 20 gallon tank at petco which came with everything. A heater, thermometer, light, lid, net, and some other stuff. I bought gravel which just look like little pebbles, a new theremometer since I prefer actual glass and some stuff to put in in such as plants, fake driftwood, bridge, and this china thing(dunno what to call it). I kept taking out the plants so they died and now I still have some that are semi dead and I'll be taking them out today. I cycled my tank with 3 black skirt tetras and returned them after it was done cucling and I found out they were fin nippers. I exchanged them for a common pleco, smallest I could find. I also purchased an orange chinese algea eater and 4 panda corydoras. I put in Yule, my male betta/fighting fish(non agressive) and I ended up giving away an agressive chinese algea eater. About a week or two ago, I found a panda floating at the top of the tank. I took him out and did a 25% water change and changed the biobag in the filter. About 2 days ago, I found another one. I'm doing a water change today in a few minutes, maybe an hour. I don't know why they keep dying and why the other two look so misserable. I feed them hikari algae wafers but I'm pretty sure the pleco might be the one eating them all since I never see the pandas eat. I want to buy at least 5 more pandas but I don't want them to keep dying. I also don't want the last two to die. I've seen the pleco get pretty agressive when it comes to anything especially eating and I've even seen him try to pick fights with my betta. My betta won't flare up or anything, just looks really scared. Do you think it might be the pleco? Or the moving that affected it? What about the FIRST fish? I dunno what to do. These are the first fish that have ever died on me. Not even the CYCLING FISH died. I LOVE panda corys and I want to keep more. Can anyone help me? Oh yes, and when they die, it's normal for them to have fuzz around them right?

eepruls

You say your tank is cycled. Are you sure? In your aquarium profile, you answer 'dunno' to ammonia, nitrite, and nitrate levels. It's imperative that you know these parameters because they tell you whether your tank is cycled and safe. You may think your tank is cycled, but unless you actually test, you cannot be sure. You may have ammonia or nitrItes in your tank and not even know it.

ABCDemily

Your betta could be killing them. Just because you say he's non agrressive, doesn't mean he is. Bettas are pure carnivores, and can be bullies in a community set up. I;d give him a house of his own to keep him happy.

haedra

There are quite a few things going on here, echoing what has already been mentioned as well.

It is imperative that you check the levels of ammonia, nitrite and nitrate in your tank. Pandas can be more sensitive than other species of corydoras, and this "might" be the cause of the deaths. Because of their being a "bit" more delicate, extra time to acclimate them might be a good idea. You mentioned you had some dying plants. Dying plant material will break down into ammonia; it will rot just like anything else in there. This could also be contributing to your problems.

The pleco is not suited for your tank. He might be small now, but he will outgrow your tank. As well, plecos are high waste producers, and this might also be contributing to your problem. Even if your biological filter can keep up with his waste production and process all his ammonia; your nitrates might be climbing too high, too fast for the panda corydoras to tolerate. I highly recommend returning or rehoming the pleco if you can.

You mentioned changing your filter media. If you were cycled, this might have thrown you into a mini cycle, or crashed it; thus your fish deaths might have again, been caused by ammonia/nitrite spikes.

As was mentioned already, the betta might be causing an issue. They can be sneaky little things; and even if you think things in your tank are "serene" he could have been doing something in your absence. I had the same situation with my own betta and some corydoras; and the only clue I had that he had been aggressive was a very, very tiny nip in one fin (out of 4 fish); and a tendency to hide all day when before it was something they never would have done. Though in this case, given the other factors, I'm more inclined to believe that the panda deaths have been a result of ammonia or nitrite poisoning.

Given all this, it will be helpful to know the following:

-Your water test results, for ammonia, nitrate, and nitrite.
-How long was the tank set up prior to the fish being added, and how many fish at a time were added.
-How your fish were acclimated, for how long

To answer your question about the "fuzz:" while there are some diseases (like columnaris or fungus) that manifest in fuzzy areas on a fish, it is likely that they were just starting to break down after death. Quarantining a fish from a store for a few weeks is always a good idea so that you don't bring home a disease to the rest of your tank. But given the other circumstances I'd have to say it is likely that they were just starting to break down after death.