Oto care, what do you think the minimum tank size is?

[DutchMuch]

i have kept otos in the past, very active little schooling fish that IMO does best in groups of 8+ if possible. But 6 is the minimum ive experienced or else they lose some/most of their social behavior.
I recently had a talk with a gentleman on a aquarium server about oto's he believes the minimum tank size should/is 10g.. and a minimum group of 4.

I had to disagree respectfully and suggest minimum 20 gallons, and a minimum group of 6.

What do you think?
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[alto]

In the wild they are most often reported as living in massive shoals (1000’s not 100’s) so would 6 individuals really provide any more “security” than 4, both numbers are far far fewer than a thousand
I do think that having similar coloured corydoras makes a difference to otocinclus comfort level

This PFK article is worth a read, especially the part where author mentions collecting trips where otos are few in number & appear as by-catches, he further mentions their possible mimetic behaviour with similarly coloured corydoras

This is something I’ve observed in a planted sale tank containing a good number of otos & pygmy corys - as the otos are sold off, they appear more & more “paired” with the similarly coloured & sized cory’s (the otos always sell quickly as they are much less available than some years ago, their price has also increased substantially)


Seriously Fish O macrospilus profile - otocinclus species are often incorrectly reported on fish sale sheets, this seems to be the species that is most common in local shops (though I don’t think I’ve ever see a farm list with this species name )
Given the small size, it’s likely 4-6 individuals would do fine in a 45cm tank (if sufficient food)

Bigger Otocinclus species, I’d be inclined to agree with a 60cm minimum tank length

More Otos always seem more active “happier” than fewer Otos, if sufficient food I’d always keep at least 6-10 and suspect 20 would be much better
But in my experience I can never seem to wean them onto vegetables (maybe this says something about the algae level in my tanks which I swear is minimal ... ) so I don’t like to buy more than 5-6
Funnily enough they seem to love Hikari frozen bloodworms & get very excited when I feed those, definitely scarfing down several bw (I usually only feed bw twice a week as I rotate foods)
Note that all local shop otocinclus are wild caught fish (I don’t know if there is much trade in domestic otocinclus)

I’ve transferred my group between a 60cm x 45cm tank and a 90cm x 45cm tank, I don’t observe much change in behaviour but both tanks are 55cm tall and 45cm deep, I believe fish are much more comfortable in tanks with more depth front to back than standard US10 & 20 gallon tanks provide

(BUT I just got an ADA 60P as it’s such a lovely tank, and has fantastic proportions (back to Amano discussions) -
I added 25 juvenile M. kubotai (today) though I’m not sure how long they’ll stay there, likely just for quarantine (no other fish in the 60P))

If fish give every appearance of thriving, it’s hard to argue that a bigger tank or more fish is “better” ...

I’m convinced that most fish would prefer to live in water with less than 20ppm nitrates (keep altums or Sphaerichthys species and it’s obvious when nitrates exceed 10 - 15ppm) but try and convince EI method aquarists to lean dose

 

[Matt @ ScapeEasy]

I personally believe that otos require quite a bit of space each both to provide sufficient grazing surface area and because they are very quick swimmers. My personal rule is one per 20 litres. I have no science behind this as such it's just from my personal experiences. Though I also agree they also prefer to be in larger groups, a group of 2 or 3 simply won't be seen as they will hide away.

 

[zozo]

I stopped using aqaurium volume as a measurement for the size and numbers of fish.. I use demensions and proportion and common sense. My personal take is a fish should at least be able to swim a bit more than it's own body size 20x in lenght of the aquarium and over 10 x the width and hieght.

Thus in my 90x35x35cm aqaurium you wont find a single fish larger than around 3cm.. Anything bigger would look sadly cramped up and out of proportion.



For an active bottom dwelling loach sp. (such as an Oto) that shows heirachical schoaling behaivor i think volume is less important than footprint. They do not care much about how much water is above them. They more need well arranged surface area with enough room and places to establish territory and find hiding places with sufficient broken lines of sight.

Hard to say how much you can keep.. In my +/- 20 gallon tank with the above demensions the way it is setup with hardscape. Lost of wood, nooks crannies and caves and heavily planted. I would say there is sufficient room for 10 to 15 oto's to live a happy live without hanging on top of eachother all the time. And can swim 30x their body size in a straight line if the wont to.

 

[zozo]

Might add mean to say, you can use wood to smartly use the height of the tank to encrease footprint with different levels semi horizontal surface arae. Than it's available surface arae is not limitied to the bottom/substrate only.. This is what i fish like an Oto definitively appreciates.

Something scaped like this but a bit more planted would be Oto heaven.

They are bottom dwelling if only given bottom.. But in a scape like this you'll find them all over the place.

 

[BubblingUnder]

I have one in a 33g (US) for extra algae control with Amano's, been in there for 2 years so doing well. I don't see him very often but he hangs around with my 8 large Sterbai Cory's. But in general the more the better, if you want to see them regularly.

 

[tam]

I've just moved my four (I've eight more in quarantine) from a 50cm long tank to a 90cm long tank and now I'm thinking a minimum of 70-80cm is really best. In the small tank they would occasionally startle and 50cm wasn't long enough for that initial 'jump' burst of speed and sometimes they'd hit the glass the far end. In the 90cm, I've seen them do the same thing, but the jump gets them about 3/4 across the tank and turns into a swim. It's a bit hard to explain the movement but I expect if you've kept them you've seen it.

I added 9 habrosus corys a few days ago and the otos have been super active shoaling with them and braver too I think. I deliberately picked the oto species with a tail spot to match the corys appearance like the PFK article described and it seems to work. Although, I think there are two different species, this pair is one and is the most outgoing, I haven't seen them again, so I have similar looking ones that have a white line above the black one then the top pattern. Can't wait to get the rest of the otos in and see them all shoal as a big group.

(Sorry, for the rubbish photo they just wiggle non stop!)

 

[Oldguy]

available surface arae is not limitied to the bottom/substrate only

Love Otos. I have six Zebras in a 20 gal planted holding tank. They will join a group of 'ordinary' & 'black otos later in the year. My Ots love large leaved plants such as cryptocoryne and anubias though they are small enough to work the leaves of stem plants. Different horizontals in the tank are defiantly of value.