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Help, Ottos losing their tails fast!

Janel R

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Hello Aquarium coop community! This is my first time sharing anything here, and I probably should have done so earlier because my story has several facets at this point. I love this community and appreciate everything you do here❤️

I’m a pretty novice fish keeper. I have one 10 gallon tank that has been set up since after Christmas of 2021. It has all live plants with two filters since I’m keeping an extra going for the quarantine tub. The only inhabitants of the tank right now are three otocinclus catfish and two assassin snails (oh, and I’ve been fighting hydra in the tank but I think that’s probably unrelated to the other issues I’m having)  

The ottos eat algae exclusively- I’ve tried spinach, zucchini and algae wafers on them and they won’t touch it.

Ammonia- 0

Nitrite- 0

Nitrate- 0-10

Hardness- very hard (off the chart)

KH- 60-70

PH- between 6.4 and 6.8

Chlorine- 0

Lights on from 8am to 8 pm with an hour break in the middle

Temp- normally kept at 78 but this is a 2nd floor LA apartment and it got up to 82 overnight, I realize that’s too hot, trying to get it down now.

  1. The ottos- Ok so back in the end of March I got three ottos to take over for my pond snails which were being eradicated by the assassins. I lost one of those on the first day of quarantine, and a second when I later medicated the display tank for my betta fish (I’ll get to him in a minute). I was left with one lonely Otto, who immediately started presenting with some fin rot and lethargy which I thought may be due to the stress of having no one to shoal with. I had to move apartments, so I let her be like that for a few weeks (no change whatsoever), and then after the move I bought three more. This time I was more cautious with acclimation, and introducing medications (again, used the aquarium co-op quarantine method). I used drip acclimation for everything. Once again, I lost one in quarantine, and two made it into the display tank. They were introduced Thursday, and OG Otto seemed to be loving having friends again. They swam around nonstop all day on Thursday grazing on diatoms, it was great. But come this morning (two days later) I was shocked to see that both the new ottos have chunks missing off their tail fins, just as bad or worse as the OG. Whatever this is, it takes over fast. They’re all just sitting around now, like OG was before they arrived. Not sure if it’s really visible in the video, but OG Otto also has some redness around her gills.

I’m sorry the pictures aren’t so clear, my phone has a really hard time focusing on fish this tiny!

  1. The betta- Just to be clear off the bat, my Betta fish passed away after we moved into the new apartment. I got him on January 29th, and at that time he already had a small tumor (I didn’t realize it was a tumor until later), and what I thought looked like some mild fin rot, but I will never know for sure because it never wen’t away entirely. I treated him with salt, and then Maracyn during his quarantine. After he moved into the display tank (mid-February) he continued to present with pin-holes appearing on his tail, some of which healed on their own, but eventually they stopped healing back. At the same time his tumor continued to get bigger, and his colors became duller and muddy. He also flashed from time to time but would always stop on his own. I removed some decor, trying to eliminate physical hazards, but nothing helped. By the time it was time to add my first Otto’s to the tank, he wasn’t looking very good and I feel bad that I probably hastened his demise, because he DID NOT like sharing the tank and I had to separate them. Soon after the separator went in (first or second week of April), I treated the entire tank with Paracleanse and then Maracyn. Again, lost the second Otto at that time, and OG still had all of her tail. Nimbus perked up for a little bit, but soon turned for the worse again. By the week of the move, he was knocking on death’s door, and I feel very bad that I didn’t have any time to get supplies to put him down humanely before he had suffered so much, but that is just how it went. You can see in his pictures that in February he was a very beautiful fish, and he slipped so far so quickly after that, it breaks my heart. I wish I knew for sure what actually killed him, but with a fast-growing tumor in the mix, I’m thinking there’s every possibility that his body was too weak to fight anything off, with or without the help of medication.

Very long story short, I need help. I’m confused, frustrated and weary of the perpetual fin rot. Should I try to medicate again? Leave it alone? If anyone has some tips, I’m all ears!


”OG” Otto, from side


OG again


the larger of my new ottos, both of these had perfectly formed tails going into the tank


littler new Otto 


full tank view


Nimbus, February 25th


April 12th, I think during medication, RIP Nimbus


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I'm not an Otto expert and I can't give advice on the meds because I don't have access to them.

But to me it doesn't look like fin rot as there is no angry red sore looking line to the tail that i would expect to see. 

It looks a bit more like general damage although who in the tank now that would cause that I don't know.

My Otto's where everywhere when I first added them then pretty invisible most days. I have plenty of algae at the back and sides of the tank though so they are behind the plants most of the time.

Sorry about Nimbus and the struggle you are having.  I wonder if the assassin snails get a bit greedy after lights out 

Hopefully keeping the water in good order the tails will grow back.

I've read plenty of tips on here about how to ensure Ottos have food from growing algae on pebbles on a window sill to add to the tank or faking it with rapashy. 

Got my fingers crossed that this turns around for you soon though

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On 5/14/2022 at 4:22 PM, Flumpweesel said:

I've read plenty of tips on here about how to ensure Ottos have food from growing algae on pebbles on a window sill to add to the tank or faking it with rapashy. 

Thank you for the well-wishes! I’m hoping they turn around soon as well. Yea I’ve heard of that feeding method, and I’ll definitely try it if I need to. For now there’s plenty of brown algae around the tank, and even in quarantine they weren’t interested in anything except what was on the walls, which where spotless to my eyes, and yet the Ottos were plump and digesting well. They are amazing little critters.

As for the assassin snails, I’ve never seen them anywhere near the Ottos, they are usually in completely different areas of the tank. My assassins are almost always on the substrate, and the ottos will hang out pretty much anywhere but there. Even if they were, I doubt the snails would be fast enough to get a bite out of one… These guys move like lightning!

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On 5/14/2022 at 6:26 PM, Mikeg said:

Could your Betta be nipping them?

The latter two Ottos never came in contact with my betta, as he unfortunately passed away before I got them. He probably got in just a few nips on my first Otto when I tried to introduce them last month- since I could tell right away it wasn’t going to work out, I divided the tank immediately. 

I know Nimbus is beyond help now, but I included his part of the story to help try and diagnose if this is a contagious thing that has been in the tank for a long time, or if all this stuff with the Ottos is unrelated.

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