Oto catfish

[saiwong]

Hello,

When I purchased my Oto catfish from my local fish store I noticed whilst some where the standard grey colour, others had yellowish heads and mouths. I decided to only choose the pure grey ones.

All is fine until yesterday when I noticed one of the Oto starting to have yellowish colour change to head and mouth. Is this normal or is colour change due to diet? I do feed Oto's cucumber.

 

[Colin_T]

Pictures of the fish that clearly show the change in colour?
Post some pictures of the other Otocinclus for comparison.

What do their bellies look like?
They should be nice and round and not sunken in. Sunken bellies is bad when it comes to Otocinclus catfish.

Have you got driftwood and algae in the tank?
Otocinclus need this and biofilm (slime on the glass and ornaments) to help their digestion.

If you don't have any algae, you can increase the lighting times up to a maximum of 16 hours per day to encourage algae to grow. You can also put smooth rocks or ornaments outside in a bucket of water and leave them in the sun. When algae grows on the rocks, you put one in the tank and let the fish clean it, then swap it for another that is outside in the bucket. You can add some aquarium plant fertiliser to the tank or bucket to help encourage algae.

 

[saiwong]

The oto catfish move & dart around very quickly so these are the best pictures I could take (without any blur)

this is the oto with yellow colourisation

and here is another oto catfish with normal grey colour

I do have algae tablets to feed the oto catfish and they also eat algae off the glass, plants and ornaments

 

[Colin_T]

I don't suppose the shop said what species of Otocinclus they were?
They look like 2 different species and they don't really look like Otocinclus going off the planet catfish website. The first pic looks a bit like a flying fox of some type but the not 2 normal types. The second pic looks like a Chinese algae eating from the picture but that is just going form the marking on the back.
https://www.planetcatfish.com/common/genus.php?genus_id=49

If they are all the same species, the yellow could be happy colouration, which is being shown in your tank and a few in the shop tank might have been happier than the others. It could also be male colouration and the fish didn't show it because it was lower ranking than the ones in the shop.

It's kind of interesting but I can't offer more info without knowing the actual species.

 

[saiwong]

I don't think the yellowish oto is flying fox since flying fox is fish like and have a mouth. Mine is loach-like with sucker mouth and sucks on aquarium glass. If you believe yellowish colour means happy fish this is all I am concerned with

 

[Colin_T]

If they are eating and swimming and acting normally, then I would just monitor the yellow and try to find out what species they are. But there are no fish diseases that cause yellow like that so it's not a disease. It's something to do with the colour of that species.