I've noticed an ongoing problem with my panda corydoras that I can't seem to figure out. Hopefully, you guys can give me suggestions. I've had a 20gal long tank for about 2 years now and it's had some problems in the past with micro-cycling so I'm a bit afraid it's going that way again and want to take preventative measures if possible.
I've got 3 panda corydoras (used to have around 6 but through long stories and much time am down to 3), 1 oto (same deal, used to have about 6 but issues over the past few months have it down to 1), 1 borneo sucker (same story, used to have 4, but lost 3), 5 white cloud minnows and 1 bamboo shrimp. The tank is fairly heavily planted with 4 medium amazon sword, 2 wisteria (1 is huge and the other is moderate) and one other I can't remember the name of. I did have a hunk of Java moss and some weeping moss as well. The Java just never seemed quite right and would explode in size and then melt away and explode in size etc. It was a huge food trap and I'd often find uneaten bits in there that were getting fuzzy so I eventually just tossed it. The weeping moss did something similar in that it looked like a fine white mold was growing in/around it and the log I had it wrapped around and no matter how often I sucked the white fluff off, it'd be back again in a couple days.
The tank has a powerhead and a 40gal filter on it with 2 air bubblers (1 machine per each stone). It's got a good deal of rocks, hiding place, mini-caves, tubes and a "rock shelf" for the bubs (fish) to hide in and around. It's got whitish play sand substrate at probably around 3/4" thick (yes I know that's probably too thick, it used to be even more because I was clueless) with some "standard" small black aquarium pebbles in 2 of the tank's corners.
The problem that spurred this all on is a number of months ago, I noticed that my largest female Panda Cory's barbels were slowly but surely getting shorter and shorter. I was worried, but didn't really know what to do, so I ended up doing nothing and her barbels basically disappeared. This seemed to do nothing to her mood at all and I know for a fact that she's spawned quite a few times even when her barbels were completely missing. No other fish were having problems, including my other panda cories so I just kinda figured she was really harsh on her face as I couldn't see any indication of fungus or anything of the like.
A week or so ago, I lost 2 otos, and a borneo sucker in the span of like 4 days so I figured this wasn't coincidence or old age and wanted to see what was up. It was then that I noticed the other 2 panda corys in the tank (both younger males) were starting to have shorter barbels as well, just like the female Panda. Spurred on by the deaths and barbels, I treated with Metroplex. That did nothing noticable and so after another weekish, I treated with KanaPlex. My wife is quite a bit more of a seasoned aquarium hobbyist so she could tell you what diseases these were meant for and I can't because I'm ignorant and don't remember, but they were tied to what we thought might've been an issue with discoloration on the dead otos as well as what might be an unseen fungus or the like on the cory's faces.
Having gone through both treatment cycles and not seeing any improvement or regression, I did a set of water parameter tests so I could ask you lovely folks your thoughts. I was shocked by the values since I typically don't have issues with the parameters in this tank (aside from a mini-cycle a year ago, before I had many plants, but that's a different story) so I immediately did a 25% water change. I didn't get a chance to post for a few days so I took the second set of tests, both of which are listed below. Please note that my PH is typically a bit high, but everything else is normal and the tank is kept heated at 70 degrees F.
Ammonia - 0ppm
Nitrate - 60 ppm
Nitrite - .25
PH about 7.2 or 7.3
Ammonia - 0ppm
Nitrate - 20 ppm
Nitrite - 0
PH about 7.2 or 7. 3
The numbers seem to be getting closer to normal, and I'll do another 25% water change tonight, but I was hoping you guys could help me think of ways to fix what seems like two, possibly related, issues.
1) The cory's barbels
2) Random water parameter changes. I feed pretty conisistently and not terribly much since I used to have a tendency to overfeed.
FYI, I normally do 2x 25% water changes a week. One on Monday and one on Friday.
Thanks for any help!