Oto's seem to come and go...

[Magnum Man]

there has been discussions before about them losing their digestive bacteria in shipping, but I'm curious as to their actual life expectancy???

most of mine seem fine, then disappear, not all at once, but typically one by one... yet I have one Zebra Oto, in my South American Tetra tank, that has been here close to 3 years, which has definitely been my longest...I've been having good luck with my other bio feeders, but the Oto family seems short lived???

 

[TwoTankAmin]

It may have to do with the basic defense mechanism of many otos. Their response to danger appears to to be to ignore it. I huess they think doing so will mean they in turn will be ignored. The problem with this method is that the oto learns it has used the wrong strategy from inside the stomach of something. So there is no learning curve at work.

Of course, this is just my theory on this. I have kept and bred a number of plecos but otos were my "bugaboo" I just could not seem to keep them alive longer term. I must have had 50, or more, die in my tanks before I decided I was being cruel to keep trying. However, I did have one in my high tech planted tank that managed to live for several years. I have no explanation for why this was the case.

I think how otos are handled from catching them to when they are sold provides an explanation. They are specialized eaters and most exporters/importers/retail sellers do not feed them properly. The result is between the time they are caught and the time they go into our tanks they are already suffering from lack of nutrition which in turns weakens them. Then add the stress of being captured bagged and unbagged, caught and bagged again etc. and it is no wonder that many do not last in out tanks for very long. This is why we often read that when looking to buy them we need to check their belly. If it is rounded and full that is a good sign. But, more often it is sunken and fish like this should be avoided.

edited for a spelling mistake

 

[Willow 123]

Having had similar experiences to the op, I have found that they need a fully mature tank with lots of biofilm and algae growing I have 4, 2 for 3 years, and another 2 I have had for 6 months.
We often get them to control an algae outbreak in a new tank and I have a theory that the algae is just that and does't contain the variety of life in it that oto's need to thrive.
I will reiterate that this is just a theory and I could be way off base here.