Buying and Acclimating New Otocinclus



One of the biggest problems of trying to keeping Otocinclus catfish is during the first month of ownership. After that, if they are still alive they should remain so unless major mistakes are made by the fishkeeper. Otocinclus start out at the fish store in bad shape.

There are countless reports of fishkeepers losing Otocinclus in the first few weeks of obtaining them. It doesn't seem to matter what type of tank the new fish are introduced to, they still drop like flies. Sometimes the entire group is lost, and at other times it's only a few. What's the deal?

Chemical Poisoning

Most hobbyists believe the trouble in keeping Otocinclus alive initially has to do with the whole capture/shipment process. Have you ever tried to net an Otocinclus among driftwood or heavily planted tanks? It's nearly impossible! Now imagine trying to catch otocinclus with a large net in a body of water filled with plants, driftwood, and rocks. That's exactly what the fish gatherers in South America are up against.

It is our belief that certain chemicals (Cyanide?) are added to the water either upstream or in a general area to slow down or temporarily paralyze these frisky little critters. The fish gatherers are then able to net them from the water in this weakened state. These chemicals could produce permanent damage to internal organs (such as the liver) and sometimes we will see hemorrhaging in the lower abdominal area in some stock.

Needless to say, I think it is wrong of the fish import industry to allow this to continue to happen, but we also are in an industry where certain fish are painted or injected with dye, or "soaked" to produce a more brightly colored fish. As long as people will purchase these fish, the industry will continue to produce them. Otocinclus are harvested in such large numbers that they remain one of the cheapest catfish (and therefore expendable according to importers) to buy. Only in serious hobbyist circles are tank-raised otocinclus considered to be much more valuable than their wild brethren. They were never poisoned so they live as long as most other tropical fish (5 years or more.)


Another reason why Otocinclus are in such bad shape in fish stores is that they are most often starving. As mentioned on the Feeding page, Otocinclus need to be constantly feeding in order to be healthy. The algae-free tanks within holding points at the exporter stations, not to mention the tanks at the store, are scraped clean on a regular basis which is not the right conditions for Otos to find some food to eat. Unless the Otocinclus are provided with vegetables (zucchini) or at the very least algae tablets at the fish store, they won't last long in the tanks there.

What can we do?

So what can we do to help get these poor fish off to a good start in our tanks? Two main aspects we need to be attention to are clean water and lots of food.

Since Otocinclus are stressed (indeed what fish wouldn't be?) from being kept in crowded fish store conditions, not to mention the ride home to your tank, it's important to keep the water they are going to live in as clean as possible. This means NO Ammonia, NO Nitrites, and very low Nitrates (<20 ppm). This can really only be done with nice large water changes done frequently.

Keeping Otocinclus well fed is also important. In the beginning they'll most likely be starving so it is important to introduce food immediately. This could be done by putting them in a tank filled with brown (diatom) algae. The excellent Little Monkeys article suggests this method. If you do not have a tank with brown or green algae then fresh vegetables should suffice.

Picking Healthy Otocinclus

It's also important to pick healthy Otocinclus right from the get go. Due to the high mortality rate with otos it is a good idea to make sure the stock has been with the fish store for a couple weeks. Although it sounds harsh, this will "weed" out the weaker ones that don't have a chance of survival anywhere.

A lot of otocinclus are in the store with worn fins, especially the caudal fin. Ideally the caudal fin should come to two sharp points on the edges, but in most cases they are rounded. This could be from stress or damage during shipment. In either case, most otos I've seen for sale have worn fins and unless it is severe don't worry about it too much. They should grow out fine if your tank parameters are good.

Another good sign is if the otos in the store tank look well fed. Ask the store clerk what they are feeding the otocinclus... if they give you a blank stare or say "Flake food" then take your business elsewhere. When the fish have nice rounded bellies it usually means they are being fed. But not all rounded bellies are equal. If the otocinclus has a HUGE belly and looks as though it swallowed a marble it's possible it may have a bacterial infection and not be overfed.


I hope this page doesn't scare you away from purchasing these wonderful fish. They are really only fragile in the beginning. If your oto lasts for over a month, chances are that it will last a good long time if properly taken care of. They really are worth the effort in the beginning, and will provide much enjoyment for a long time thereafter..

Back to Main