Отоцинклюс макроспилус

Totally no beginner fish, although it is presented as that. We got 7 Fish at first. One starved because he had organ failure since we got him. One got a mysterious infection on the head and another one died by unknown cause, but i remember one of them also getting very thin, so i think it was him. One day after we got them i discovered that they are a lot harder to keep and I tried my best to keep everything fine. Still 3 already died in the first month and i don't give the others much chance. They should be kept in large numbers but i wont buy our remaining 4 some buddys its just not worth it.