Some 30 months ago, I popped a shoal of 6 Otocinclus into the CT. Some 12 weeks later they had all vanished, and I wrote off that species as being unsuitable for my tank. However, over the weekend, while doing the weekly water change , who should pop up at the back of the tank but a survivor. ! I only spotted him as the plants have thinned out; so I immediately dropped in a couple of Algae pellets as his/her belated Christmas pressie.