Otos Dying After Months Of Success

Ian Chan

New Member
Mar 28, 2018
Hi there,

My otocinclus (standard ones) have been dying one by one.

I started with 12, 5 months ago in July. 1 passed away in quarantine and I experienced no deaths for almost 3 months after. However, for the past 2 months, I've lost 3, one by one. The symptoms are always the same: very skinny stomachs and red, translucent skin. I suspect they're starving to death - but I don't know if the starving is food related or a disease/ailment/poisoning. Those which get these symptoms then die are always the smaller otos, the larger guys are always full-bellied. Oddly, at any one time, most of the otos are full bellied with 1 or 2 skinnier than the rest. And when the skinny one passes, it's almost as though another takes its place.

For feeding, I provide repashy super green which has no meat and they usually take to it relatively well, although the larger otos and shrimp seem to take it more than the smaller otos. Even when I feed excessive amounts of repashy gel, the smaller otos rarely seem to eat them directly, always hanging out near to the food but not munching directly. Rachel O Leary vouches for Repashy for her hundreds of otos.

I'm worried about my otos, esp since they're social fish and appear to be more active and happy when there were more of them. Its possible that there'll be a cascade of deaths since they eat more readily when there were more of them.

Admittedly, I didn't get a good stock of otos, and they were malnourished and had dull colour when I purchased them. I heard that many otos have cyanide poisoning due to the capturing process so I wouldn't be surprised if that contributed to their deaths.

Brown diatoms are probably the best food but I don't know how to grow and feed it sustainably. Further, it may be Poisoning or a disease causing the deaths. Maybe it's CO2 contributes my CO2 but its 30 ppm maximum.

If you have any tips, pls do share them! Thanks in advance

Water parameters:

Tank size: 15 gal
pH: 7.4 (w/o CO2)
Tds: 200
Temp: 25C (chiller keeps it constant)

Skinny otos :(
WhatsApp Image 2018-11-28 at 8.06.48 PM.jpeg

WhatsApp Image 2018-11-28 at 8.06.49 PM (1).jpeg

Healthy fat oto (clear stomach bulge)
WhatsApp Image 2018-11-28 at 8.06.49 PM.jpeg

Otos during feeding (repashy in the corner)
WhatsApp Image 2018-11-28 at 8.06.49 PM (2).jpeg


Lifetime Member
Lifetime Member
Jun 3, 2013
Hi Ian, from the pics and my experience I think you are correct that they aren’t getting enough to eat. Otos and shrimp tend to compete for algae and biofilm, so they may not be getting enough. I would suggest trying some other foods. I use Lowkeys Ultra Supple and mini algae wafers, to give them a variety. Can also supplement with veggies like cucumber, peas, zucchini, etc if they will eat it. I had the same problem with them until I found a food they liked.


New Member
Jan 21, 2020
Well they look hungry.

I would try zucchini.

Buy one.
Cut it up into slices.
Remove from boiling water.
Let slices cool.
Transfer to a ziplock bag.
Pull one out and drop it in the aquarium.

After a minute or so the zucchini will drop to the bottom of the aquarium and provide a great meal. Remove any remaining zucchini and the skin after ~24 hours, or less if you choose.

Hope this helps.