Zebra Otos (O. cocama) disappearing

[tinyfish]

Hello!
I was wondering whether anyone here may have had a similar problem - I had some Zebras about a month ago. They looked in good condition and had been in the shop for over three weeks before I had them. Despite this, and splitting the batch into two lots and two different tanks at home (both well established and heavily planted, one three one two foot) and feeding plenty of Algae wafer on top of the normal food for the other fish (all small and peaceful) I lost at least two thirds of the fish, with no obvious signs of disease, or, in fact, bodies. Found one set of bones only. Also did my water changes meticulously. The remaining Zebras are lively and all of my own fish also seem in good spirits. I am at a loss and would be grateful for any ideas!
Tiny

[Yann]

HI!

Have you tested your water and what are the different water parameters??

Cheers
Yann

[MatsP]

What's the temperature in the tank? Oto's are generally more cool water than the average tropical tank.

The cat-eLog for

Otocinclus cocama

says that they should be at 21-25'C.

Warmer water makes fish "age" quicker, and Oto's are, as I understand it, pretty short lived fish anyways.

What I wonder is where your "bodies" have gone. It would seem that if you have fish dying, you should find bodies. Ok, so you've found bones, which means that something ate the meat off the body, but if you have had two thirds die, you should have been able to find the bodies. Are you sure there's no big fish in there that you forgot about...

--
Mats

[tinyfish]

pH is seven, sometimes just under in the one tank, just above in the other , water is very soft in both. Nitrite always zero, Nitrate very low (I forget the exact numbers, can't check as in work at the moment).

The temperature is 24/5 in the one , 25/6 in the other. They disappeared within a month, so I don't think it would have been old age. (I hope not!)

Certainly no big fish, I keep Heterandria formosa, Rasbora maculatus, baby Guppies, Ember Tetras, pigmy Corys (only 3) and young Ricefish in those two tanks. The bigger tank has some Erethistes catfish also, but they are not aggressive as far as I am aware. Lots of baby fish everywhere.

Thanks for your help so far! That was really quick!

Re. bodies, I suppose the Guppies and burrowing snails may have taken care of those, and there are so many plants the corpses may be difficult to spot (the bones I found were right at the front and gone the next day).

[Mike_Noren]

What do you feed them (because you ARE feeding them, right)?
They're sensitive to bloat if given too protein-rich food. I've personally killed ten zebra otos by feeding them bloodworms.

[metallhd]

I lost a couple of otos once due to a dead platy stuck in the plants, had done water change but the ammonia levels were way high due to the decomposing fish, once again in a heavily planted tank . . . I'd do some fishing around in the plants . . . sorry to hear about your loss

[tinyfish]

I do give the other fish chopped bloodworm once a day, usually in the evening, so that the Erethistes get some as well. I have never seen the Otos eating the bloodworm but if that is what killed yours, that may be an explanation for my losses, because I let some of the bloodworm fall to the bottom on purpose where they could get it without me noticing (not enough to pollute the water, but enough for the nocturnal fish).

The other feed (usually morning) is flake and algae wafer, usually I put a bit of algae wafer in at night at well (again for the nocturnal bottom feeders).

I do not think there are any corpses anywhere (had a good look for my otos and would have found the corpses then), also I lost otos in two separate tanks at similar rates.

Thanks for all your ideas!

Mike, when you lost your zebras to bloodworm, were you giving them alternative food as well and they still picked the food that killed them, or were the bloodworm the only food at the time?

[MatsP]

Mike, when you lost your zebras to bloodworm, were you giving them alternative food as well and they still picked the food that killed them, or were the bloodworm the only food at the time?

Just like us humans, fish don't always know that "too much of a good thing" isn't good for them, so they may well eat all the bloodworm that they can, even tho' you've supplied some other food that they would also eat.

If there's bloodworm available, I'm sure most fish that are able to eat bloodworm WILL eat them.

--
Mats

[Yann]

Hi!

By re reading your first post, it aslo seems you did not quarantine them before adding them into your tank...

Maybe the died form a disease outbreak, such as a bacterial infection

Cheers
Yann

[Mike_Noren]

Mike, when you lost your zebras to bloodworm, were you giving them alternative food as well and they still picked the food that killed them, or were the bloodworm the only food at the time?

They love bloodworms. Eat it like spaghetti. I gave it to them in an attempt to get them to spawn.
Within days the first ballooned and died, then one after the other until all ten were gone. Other fish in the tank were unaffected. I still have a photo somewhere of a grotesquely swoollen zebra oto - it looked like an eggbound female, but it had red lines (bleeding) around the anus.

To be fair I don't know for sure that it was the protein of the food which killed them, or if the bloodworms had not been handled properly before I bought them, that they had started to rot before being frozen. Some aquarists I've talked to have also had unfortunate experiences with that particular brand of fishfood (with Tropheus, another plant eater).

Anyway, nowadays I never feed protein rich food, especially not bloodworms, to plant eaters, and, for what it's worth, I've not had any cases of bloat since.

This is all anecdotal, take it for what it's worth.

[bronzefry]

I've stopped feeding the tank with Otos and the Chaestoma bloodworms. I fed them once, because the Cories in the tank love them. After that, never again. The Chae had one worm in its mouth for at least a day. The Otos wouldn't stop eating them and became extremely bloated. I now give them frozen tubifex once a week. They still suck it up like angel hair! In a 75 gallon tank, one cube lasts 30-60 seconds. I'd say the Cories get the majority of it. I've never seen them eat so fast. The Chae gets a few. The Otos get about one each, on average.