I have 3 small plecos now, one is 7.5cm, 8.5cm, and largest of all 9cm. This problem started about two weeks ago when they stopped eating normally. I would add a slice of cucumber everyday and they will turn the slice into skin under 24hours. But now they eat slowly, they finish one slice of cucumber in two days! Then last week I noticed something wrong with the 8.5 and 9cm one. They often swim up poking their nose above the water surface. Since then the two of them always stay up there. Then yesterday the 8.5cm one died so I am worried. And one last bit, I also noticed small white spots(like scratches) at the joint of their pectoral fin. Is there anything wrong? They are not stressed as they're colours are very black.

Help please? I don't want to lose my plecos.

Wow...how long was ur last water change ?
Guess nobody told u tat u cannot leave the cuke in the tub for more than a day ?
Make sure u make daily water changes coz plecos tend to crap more than any fish...if can keep them in a bare tank to aid in cleaning their poop.

I've had no problem with them in a bare tank with 25 plecos in there...
Problem only started when i moved them to my gravelled tank...

Key point to note...good water quality is the best assurance to good health