The next day, he was sitting at the entrance to one of the PVC pipes that I have in the tank for shelter, until I get proper-sized breeding caves for them. He was wiggling his tail all day long, nonstop, but what was different was that sitting outside of the pipe, in the curved part, was a 2nd pleco, who was also wiggling its tail.
Later that day, I was working on covering the filter intake and powerhead with a mesh screen. Bit of context: 2 weeks ago, I had introduced a school of tiny little harlequin rasboras to the tank (without quarantining...) and the morning after, I had discovered that 5 of them had perished after getting stuck inside the filter intake and the powerhead, and a 6th had made it through the filter and was inside the filter itself, very much alive. Saved him, and immediately got some fabric to cover up the filter intake and powerhead so that the remaining fish would never get caught inside. Only early this week had I realized that the holes in the fabric were much too fine, and it was severely impeding water flow in the tank. The powerhead was not pushing much water through, and the filter was not sucking up much either. So, essentially, all water movement and filtration systems were running at only a fraction of their efficiency, for at least 7 days. After discovering this, I went on the hunt for a suitable sized mesh screen: one that had holes large enough that it would not impede water flow, but small enough that the tiny rasboras could not possibly fit through. So, fast forward back to 2 days ago, and after pointing a desk light at the powerhead so I could see what I was doing while attaching the screen, I noticed in the light that the original tail-wiggling pleco looked a little unusual: he seemed to have spots on him, that were either just odontodes in the light, or white spots from the dreaded ich, which I have never experienced before, so I don't know whether it's that.
As soon as I saw that, I took a picture and posted it on another forum. A member asked if I had considered that it could be velvet, rather than ich, which I hadn't even thought of.
Last night, before turning the lights off in the room, and after I had dropped pellets into the tank, I noticed that all 4 of the plecos were out and about, which was unusual for when the lights were on. Normally, they sit in their usual places, only somewhat visible, and sometimes reposition themselves, but otherwise do not stray from their locations until after all the lights are off in the room. One of them was in his usual spot, but was wiggling around a bit more in view, and the other 3 were just roaming around. One of those 3 is one that had damaged pectoral and pelvic fins when I received him/her, which allows me to identify it easily. That one was darting around the entire tank, swimming from one side of the tank to the other, then going halfway up the side glass and suctioning to it for a moment, then going right back to darting around. Highly unusual, unless it had gotten spooked by something, but I have no idea what it would've been. They were also starting to do this thing where they wag their tails back and forth like a happy dog. All 4 of them this time.
This morning the damaged-fin pleco was moving from hiding spot to hiding spot, but not erratically this time. All 4 plecos were, and still are, wagging their tails constantly. I took a good look at the damaged-fin pleco, and to my horror, it looked as if it were covered in tiny ich-like spots. The pleco who was the first to wiggle his tail and also was the one who had signs of ich still looks the exact same, no better, no worse. His doesn't look very bad, and I'm not very concerned about him. The other two plecos look normal, aside from tail wagging, and the rasboras are behaving normally with zero signs of ich, velvet, or other illness.
I did a 40% water change an hour or two ago, and plan on doing the same thing tomorrow. Around 20 minutes after the water change, I took two pictures of the pleco with damaged fins and possible ich. These two pictures are the same fish:
The tank is 20 gallons, 30x12x12", heated to a constant 80F, equipped with a Koralia Nano powerhead pump and Aquaclear power filter. pH of 7.2, same as it comes out of the tap, GH/KH unknown as I have never tested for it. Not sure where my water testing kit is right now, but last time I tested this tank, which wasn't too long ago, the ammonia was 0, nitrite 0, nitrate around 20. 30% water changes done every 10 days or so, but I hope to stick to a weekly routine. Tank has no substrate or plants, and contains the 4 L134 plecos and a school of 15 tiny rasboras, which are all fed Tropical-brand discus pellets every night, and OmegaOne freshwater flakes in the morning for the rasboras specifically. The plecos have been in the tank for around 4 months, but the rasboras were only added 2 weeks ago and unfortunately were not quarantined (I did get them from a quality LFS who I trust, but of course that doesn't mean they are always 100% disease-free...). No medication has entered the tank in its entire existence.
I think that's all the info I've got. I'm hoping you guys can help me out here. The only disease I have experienced was bloated Tropheus (african cichlid), which was quite a bit different, so I don't know what to do here, plus the fact that this is the first time I have ever kept plecos, though I have done lots of research. Thanks for your time.
