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I have 9 Otocinclus vittatus or vestitus in a 10 gallon planted tank on my desk at work. I setup the tank in July of this year. I acquired the fish from PetSmart here in the US. I have a common HOB filter with a sponge prefilter on it. Heater is set at 75F. 20W flourescent bulb on an 8 hour timer. Weekly 50% RO water changes. pH=7.0, GH=4, & KH=3.

If you were to look at the tank, you wouldn't even see the fish unless they were startled by movement outside of the tank. Normally, they just hang out on the lower leaves of a Crypt wendtii or directly underneath the plant. This plant is directly in the path of the water current leaving the filter's outake. I always just assumed that they didn't care for a bright light shining down on them and liked the current.

When I arrived at work today, the water level was about 1/2" lower than I like to keep it, so it was making a louder sound than usual. I unplugged the filter so that the sound didn't disturb my coworkers. Immediately, the fish came out from underneath the plant and started swimming around the tank, mostly as a group. They seem much happier and hang out on the glass a lot. I like this change of behavior.

Does this sound like normal Otocinclus behavior? I don't think too bright of lighting is an issue. Did I have too much current? Why would they hang out in the current underneath the plant? Should I switch over to an air driven sponge filter and point the current more diagonally across the tank as opposed to the HOB current that goes from back to front, top to bottom in direction?

I would love for this species to spawn for me someday. All advice is welcomed.

Thanks,

I haven't noticed any peculiar behavior when it comes to current. Light on the other hand, I have seen. They will always try to minimize exposure to a bright light source. One thing you can do for your filter is to add a diffuser to the outflow. This will aid in reducing the current. I make them by cutting a small gatorade bottle to size to match the outflow. Works wonderfully and pretty much use them on all my tanks.

Thanks, James! Would you happen to have a picture or a link to a picture of the diffusor to share so I can get a visual?

Let's see if this works:



You can see it under the Riccia carpet. Cut the middle section of the bottle out and then cut the area where the glue is to make a "C". You'll need to cut it down to size to fit your filter's output length. It's probably going to be around 2 3/8 there abouts if memory serves me right.

I see where you are coming from now. Thanks a bunch, James!

My Otocinclus have the same behavior as yours, but I have 5 otos. These fish live in a, as I have read, current rich habitat, but during the other seasons live in a almost current devoid habitat. I'm pretty sure they breed during the current devoid stage, so keep that riccia carpet on for a while, good luck with those otos!