what to feed otocinclus

Last updated: September 28, 2022

Though I’m not an expert on catfish, I’ve picked up quite a bit of info on Otos over the last couple of years. Much of this has been from looking them up on the internet (planetcatfish.com is a good resource), but quite a bit has been learned from watching these algae vacuum cleaners each day for a few years.

“What can I do to get my Otos to notice the algae disk?”
This is one of the first questions new Oto owners ask when their fish totally ignore the food that is offered. Since all other fish need to be actively fed, some people might start to worry that something is wrong.

A Zebra Oto © Becki Once they clean up any visible algae in a tank, there is still algae and other organisms on plant leaves and tank surfaces that the Otos will eat. It is a good idea to supplement their diet with vegetables, but algae disks or wafers seem to be ignored by almost all Otos. When I had some newly-imported zebra Otos shipped to me at work, I was ready for their arrival with a small plastic tank, some algae disks, and a strip of seaweed. Since they were recently imported, the Otos were very thin, and I figured that they would munch on the algae disks until I could get home and cook up some zucchini. The Otos didn’t even touch the algae disks, but nibbled a little on the seaweed. When I got them home, they pretty much immediately started munching away on the zucchini I placed in their tank.

Since it seems the common experience with these fish is that they shun algae wafers, it’s probably best to go with fresh veggies or seaweed sheets as a supplement to their diet.

Another common question is ‘What should I feed my Oto?’ The most common veggies used are cucumber, zucchini, pumpkin or other squash, leaf lettuce, and spinach. I’ve also seen peas (with the outer ‘shell’ removed) and broccoli mentioned, but in the couple times I tried feeding these to my fish, they were largely ignored by EVERYONE in our 3 community tanks. Your results may differ, and if you stick something in and they seem to like it, make a note of their preferences and go with that. All veggies should be blanched, or in other words, place them in a cup of water, and place it in the microwave for about a minute for leaf veggies, 2 minutes for sliced veggies. Let cool before sticking it in the tank. Leaf veggies can be anchored with a lettuce clip that’s available at most pet or fish stores. With sliced veggies, I just stick it in the gravel to anchor it.

To see if the Otos had any preferences, I set up a veggie buffet in my 2 tanks that have Otos to see what would happen. The veggies offered were cucumber, zucchini, acorn squash, spinach, romaine lettuce, and a strip of seaweed sushi wrap (it’s about the same thing as what you get in the pet stores, the only difference is the stuff for fish will sometimes have added nutrients). The spinach was the only thing that they seemed to ignore, and the zucchini was slightly more popular than the other veggies. In one tank, our platys and guppies ate the seaweed strip before the Otos had much of a chance to try it. The Otos that we have had longest hardly paid any attention to the veggies, while the zebra Otos we have had for just over 2 weeks now were more frequent diners. So, what you feed your Otos can be guided by what you’re having for dinner that week, although it’s a good idea to vary their diet by offering different veggies now and then.

Since the more acclimated Otos seem happy to graze the free food provided by our tanks, you could probably get by with feeding veggies once or twice a week. Veggies should only be left in the tank for 24 hours, since if they are left in much longer they will start to decay, and be a pain to try to remove from the tank. If your Otos are constantly clinging to the veggies, or they don’t have the typical ‘pot bellies’, it may be a sign to increase the frequency of supplemental feeding.

Some people feed their Otos fruit as well, but I’m a little hesitant to introduce something with higher levels of sugar, since I don’t think its part of their natural diet. For the same reason, I don’t try feeding them leafy herbs such as cilantro, and I stick to the more ‘bland’ veggies. If you do want to treat your Otos to fresh fruit, I’d recommend doing so VERY sparingly. If someone has been feeding their Otos fruit for years with no ill effects, please let me know and I can update this information.

Another method I use to feed my Otos is to ‘farm’ algae on slate pieces (or tank ornaments, or plants) in other tanks that don’t have algae eaters, and occasionally switch out the algaefied furnishings with the newly-cleaned ones. If you quarantine your new Otos before introducing them to the main tank, this method along with feeding them veggies is a good way to ensure they get the nutrients they need.

Eenie, Meenie, Miney, Moe…How to select the best Otos.
Many people think Otos are hard to raise, since often some will die soon after they are brought home. What I believe are the 2 major reasons for this (unless you have Otos that quickly develop a bad case of ick or other detectable illness) both relate to food. The lack thereof. When Otos are freshly imported, they have been deprived of food for who-knows-how-long. When mixed with a pet store that keeps their tanks completely algae free by mechanical or chemical means and doesn’t feed them fresh veggies, these poor fish are often literally starved to death. The stress of yet another move to a new tank may be too much for some, even if proper food is plentiful in their new home.

To ensure your Otos have the best chances of survival, check to see if they have potbellies. The plumper the tummy, the happier the Oto, in general. Unless they have several batches of Otos in, all should have about the same ‘girth’. If possible, get them from a trusted local fish store as opposed to a larger pet store or a mega-mart. Get them from a store that has veggies in the tanks, so that you know they’ve had enough food at the pet store to keep them healthy. Find out how long the Otos have been at the store- the longer they’ve been there (as long as they’ve been properly fed), the less of a chance there is they’ll die when you bring them home.

If the above options are not feasible because of the lack of good fish stores where you live, or you are getting harder-to-find Otos in the mail, the best you can do is to get a few more than you optimally want, and place several slices/leafs of veggies in the tank. One batch of zebra Otos I received in were so thin I could see their ribs, but with generous portions of zucchini daily, all are still alive, healthy, and are on their way to big bellies. If after several weeks all the Otos live, and you decide you have more than you really want, rejoice that you have a healthy batch and pass them on to a fellow aquarist who can use a few. Personally, I can’t have too many! Otos should do OK by themselves, but prefer groups of around 3 or more.

The second major cause of Oto loss usually occurs a few weeks to a few months after they’ve been in their new home. If not given vegetables or seaweed sheets as a supplement to algae, they may clean the tank to the point that it’s no longer able to sustain the number of Otos it originally did. Plecos and other algae-eating fish may also compete for food. I have seen a few different recommendations regarding stocking levels of Otos. Since tank conditions (and tankmates) vary widely, the only stocking limit you should worry about is the general tank limit. If you feed them their veggies, you should be able to have as many as you want. Just make sure to increase feedings if they start to constantly cling to the veggies as opposed to the occasional nibble. Keep an eye on their tankmates, to ensure others aren’t hogging vegetables or scaring the Otos away from them. If you have fish that are competing with the Otos for the veggies, place several slices/leafs in different areas of the tanks to make sure everyone’s happy.

The Oto eye for the aquarium guy (or gal)
According to planetcatfish.com, live plants are essential for the long-term survival of Otos. I don’t have enough personal experience to back this up, but live plants can’t hurt! Even if you don’t have the optimal setup for plants, through research online and maybe some trial and error you should be able to establish at least a medium-density planted tank. After a fair deal of trial and error, I was able to find a variety of plants that would live in a tank with standard lighting, no co2, and even an undergravel filter – with a powerhead no less (usually seen as a no-no for planted tanks since it causes problems for some plant’s roots). This was before it dawned on me to actually do a bit of research to see how to get my plants to stay alive! If you don’t already have plants, do a little bit of research to find out what should grow best in your tank. You can buy plants at a local fish store, from an online source, or post a want-ad in petfish.net’s trade/sell board. If you don’t mind bringing up the plants from smaller cuttings/baby plants, you can usually find someone who is willing to go through their tanks and see what needs pruning/thinning. Also check to see if there’s a local aquarium club near you, they will usually have auctions or mini-auctions where you can pick up lots of good plants cheap!

Driftwood and vertical sheets of rock (preferably slate) are also mentioned as furnishings for Oto tanks. No specific reasons are given, but it’s my guess that the porous rock allows for more algae to grow, or provides a better surface for the Otos to cling to than the side of your tank.

Oto Antics
Before we got Otos, I thought only cories would rush up to the top of the tank to ‘gulp’ air. Watching our first batch of Otos acclimate to their new home, I was surprised to see them do the same. While they are usually not the most active or attractive fish in the tank, it can be fun just to sit back and watch them eat algae off of the front of your tank, or perch themselves upside-down on the underside of a leaf for a quick snack.

Oto Links and Resources on the Web
Catfish_And_Loaches/oto.php (has the technical Oto info- temp, ph, etc.)


http://www.planetcatfish.com/core/index.htm (click on ‘sort by scientific name’, scroll down to ‘O’)