I have a ten gallon tank with 2 otocinclus, 3 neon tetras and 3 zebra danios, Iíve had one oto for almost 2 months and the other one for a little more than three weeks, and that one is quite sluggish and lethargic, theyíve both gotten more lethargic over the last few days but the ďolderĒ one less so. All of my other fish seem healthy and my tank is about 8 months old and well established. The pH is good, I donít have a way to test nitrites, but once a week I treat for it and my nitrates have been between 20-40 ppm
. Both of them eat spinach and algae and I donít know why theyíre so lethargic!