Otocinclus observation

[tolstoy21]

I could be crazy or speculating but I just noticed something these past few weeks . . . . 

I have a moderately planted 125 gallon. About two years back, when I set it up, I moved about a dozen otos into it. Over that time, their numbers appeared to dwindle.

I re-scaped the tank about 6 month ago and as the new plants were settling in, I had a large algae outbreak so I figured I'd replace my missing otos. I went to my LFS, got a dozen more and added those into the tank.

Since I've added these new ones, it appears the others were there all along, just hiding and not very active. However, now I just counted a school of over 20+. I don't have any aggressive fish in this aquarium that would force anything into hiding in my experience, nor anything that's much larger than an oto. Zebra Danios are probably the largest fish i currently have in that specific tank.

So what I'm observing in my tank at least is that they appear to be more highly active in this larger school (20+ members) and eating more algae. Obviously there's more of them so of course more algae gets consumed. But I never saw the older ones grazing at all, and this this lead me to the impression that I only had 2 or so left in the aquarium.

Am I crazy, or has anyone else had experience with this? Do larger school numbers encourage more activity in terms of not hiding as well as actively consuming more? For me I'm going to speculate the tipping point was getting the school above a dozen members.

Before I upped the numbers, algae was overtaking everything. Every surface was coated. A week after upping the oto numbers, the algea was completely consumed. 

Why were the original dozen so reclusive and apparently not very hungry?

[Paul]

I don’t think your going to get a conclusive answer. There are so many variables like foot traffic patterns around the tank, lighting strength and or length of time, activity of tank mates etc it would be difficulty to pinpoint one thing that would cause them to hide. I have Ottos in all my tanks the most being 4 in a 120 and they’re out all the time granted you have to look for them occasionally but they’re out and eating.

[bcflowerlady]

I have watched a video when Cory and Dean were discussing Peru. Appears Otocinclus are schooling catfish in the wild and can be found in groups of hundreds to a thousand. I imagine that having 20 has triggered their herd instinct. I'd love to see some pictures. I imagine they are quite the sight all together.

[Phill D]

My nearby LFS has (shockingly) lots of otos at a time and in large numbers they do like to school together and nap in the same place. Even mine (i only have 3) very often sleep in the same spot near each other. When they go grazing they tend to do their own thing most of the time (in large numbers this probably changes). I've also read that they are comfortable foraging alone but when spooked they look for the shoal. And, additionally (adorably?) i've read shoals of otos with group together with shoals of corys. That's something i want to see. 

[JerseyBundy]

I bought 4 otos back March. 1 died and 1 gave me oto fry. Since she's had the fry. I don't see her or the original males as much. But the fry aint fry now and every morning they school in front of the glass. Cool to see. Im not sure how many I have.  There was over 40 oto fry. But I see over 20 now but who knows.  They hide very well. 

[mouseturd13]

my 6 ottos all like to hangout together under the sponge and don't seem to come out until night time. The only other fish I have are some zebra danios that don't bother the ottos, but I guess maybe they just like peace and quiet lol

[Tetra Guy]

I thought I had lost a few Ottos, but they were hiding.  Unseen for months in a heavily planted but only 10 gallon tank!  I added new ones meanwhile, noticed the older ones had turned shades of brown, while the new ones are grayscale.   The old ones went back to hiding.  New ones tend to be in the general area of each other, perhaps they maintain visual contact for safety.

 

[Streetwise]

Otocinclus are very shy, but sometimes you get to see them basking on leaves. Chill tank-mates help.

[Marc]

They definitely like company my 6 usually hang out near each other, but not super close. I bet they would like as big school as the tank could support. I don't have a hard time finding them in my 55. I think about 10 would be a good number.

My 2 guesses or maybe a combo guess.

1. Something in your tank was making them uncomfortable.  Danios can be aggressive towards other fish. My most dominant one would chase tetras and eat any babies my swords or guppies had. Or something from outside the tank spooks them. 

2. They got their fill of algae at night with all the algae around and didn't have to come out in the light. When you added more they have to work more for their food.